Curtain Terms Glossary: Headings, Lining & Fit | Ona
Updated October 2026 · By the Ona team · about 18 min read
The short answer: curtain listings use about a dozen words that actually change what you buy — panel (one piece of fabric), pair (two panels), flat width (the width of one panel before it gathers), fullness (flat fabric ÷ rod width), heading (how the top attaches to the rod), lining, opacity (blackout, room darkening, light filtering, sheer), drop or length, return, overlap and stack back. Everything else is hardware or decoration. This glossary gives one plain definition per term, in US inches, plus the number or formula each term changes.
The eight that cost people money - Panel = one curtain. A pair = two panels. "2 panels" means you get two. - Listed width is flat width, per panel. A 52″ panel does not cover 52″ of window once it gathers. - Fullness = total flat fabric ÷ rod width. 2× is the normal target. - Drop (UK) = length (US). Both mean top of fabric to hem. - Blackout ≠ a dark room. It describes the fabric, not the light that leaks around it. - Room darkening is not blackout. It is a lighter grade, usually unlined. - Return is the few inches of fabric that wrap back to the wall. - Stack back is the wall space your open curtains eat.
Use it with the curtain measuring guide when you are ready to measure, or the curtain calculator if you already know your rod width. To see the words on real products, shop all curtains.
How to read a curtain listing in 30 seconds
Four questions, in this order. Everything in this glossary hangs off one of them.
- How many curtains am I getting? Look for "pair", "set of 2", "1 panel" or "single". See Panels and pairs.
- How wide is each one, flat? The first number in "52 × 84" is the flat width of one panel. See Size and fit.
- How does the top attach? Grommet, back tab, rod pocket, pleat or wave. See Headings.
- How much light does it stop, and is it lined? See Opacity and lining.
The numbers behind the words
| Term | The formula or number it controls | Worked example |
|---|---|---|
| Fullness | total flat fabric ÷ rod width | 2 × 52″ panels on a 52″ rod = 104 ÷ 52 = 2.0× |
| Panels needed | (rod width × 2) ÷ one panel's flat width, rounded to an even number | 76″ rod → 152 ÷ 52 = 2.9 → 4 panels (2.7×) or 2 × 70″ wide panels (1.8×) |
| Rod width | window width + 6–12″ per side, measured end to end without finials | 60″ window + 8″ each side = 76″ rod |
| Length, float | floor-to-fabric-top height − ½″ | 84½″ from rod to floor → order 84″, hem floats ½″ clear |
| Length, kiss | floor-to-fabric-top height, exactly | 84″ from rod to floor → order 84″, hem touches |
| Length, puddle | floor-to-fabric-top height + 4″ | 92″ from rod to floor → order 96″ |
| Return | your bracket's projection, wall to rod center | 3½″ bracket = 3½″ of return each end |
| Center overlap | 2–4″ of fabric crossing in the middle | Two panels meeting = ~3″ overlap, fewer light gaps |
| Stack back | the open panels' gathered width, each side | Measure it once hung; a gathered grommet panel is roughly a third of its flat width |
The rule of thumb, if you only remember one thing: rod runs 8″ past each side of the window, total flat fabric is twice the rod width, and the length is measured from the fabric top, not the rod.
Panels and pairs
Curtain panel. A curtain panel is one piece of finished fabric with a heading at the top and a hem at the bottom. One panel covers one side of a window.
Pair. A pair is two matching panels sold together, one for each side. "Set of 2", "2 panels" and "pair" all mean the same thing.
What "2 panels" means when buying curtains. It means two curtains arrive in the box, one per side, and the listed width applies to each panel, not to the two of them added together. Two 52″ panels are 104″ of flat fabric, which suits a 52″ rod at 2× fullness — not a 104″ window.
Single panel. A single curtain panel is one curtain sold on its own. It is the right choice for a narrow window, for a one-way draw across a door, or when you want to combine an odd number of panels across a wide run. Ona sells one single: a 70″ wide grommet panel.
Wide panel. A single panel made much wider than a standard one, so one piece covers what normally takes two.
Double curtains. Two layers on one window — usually a sheer or light-filtering layer at the back and a heavier layer in front, on a double rod. Ona does not sell double rods or sheers today.
Dress curtains. Panels hung purely for looks that never close. They need far less width, because they only ever sit stacked at the sides.
Day curtains / night curtains. Informal names for the two layers above: the day layer filters light with the room still usable, the night layer closes for darkness and privacy.
Half curtains / café curtains. Short panels covering only the lower part of a window, usually on a rod across the middle. Ona's shortest length is 63″, so no Ona panel is a half curtain.
Curtains vs drapes. In US usage, "curtains" are lighter, often unlined, and sold ready-made in standard sizes; "drapes" are heavier, lined, often pleated and usually floor length. The words overlap constantly and no size or opacity is implied by either. Everything Ona sells is a ready-made panel, lined on three of four styles.
Headings
The heading is the top edge of the panel and the mechanism that attaches it to the rod. It sets the fold shape, how easily the panel slides, and how high the fabric starts relative to the rod.
| Heading | What it is | How it hangs | Rod or track | Sold by Ona |
|---|---|---|---|---|
| Grommet (US) / eyelet (UK) | Metal-rimmed rings punched through the top hem; the rod passes through them | Deep, even, slightly stiff waves; slides easily | Rod only, and the rod must be thinner than the ring's inside diameter | Yes — grommet pair, wide panel, velvet pair |
| Back tab | Fabric loops sewn on the back of the heading; the rod threads through them, hiding the hardware | Soft, even folds with the rod concealed behind the fabric | Rod, slim | Yes — back-tab pair (also has a rod pocket) |
| Hidden tab / concealed tab | The same thing as back tab; the tabs are invisible from the front | As back tab | Rod, slim | Yes (same panel) |
| Tab top | Fabric loops on the front of the heading, visible above the rod | Flatter folds, visible loops, rod on show | Rod | No |
| Rod pocket (US) / pocket curtains, slot top (UK) | A sewn channel across the top; the rod slides inside | Tight gathers; stiff to open and close by hand | Rod | Yes — the back-tab pair doubles as rod pocket |
| Pinch pleat | Fabric pinched into groups of 2–3 at the top and stitched, hung on hooks or rings | Crisp, tailored, evenly repeating pleats | Rod with rings, or a track with hooks | Not yet — preview only |
| Goblet pleat | A pinch pleat with the top opened into a rounded cup | Formal, structured | Rings or track | No |
| Pencil pleat | A gathered tape heading pulled tight into narrow upright folds | Dense, soft gathers | Hooks on a track or rings | No |
| Ripple fold / wave / S-fold | A carrier tape on a special track holds fabric in a continuous S curve | Uniform soft waves, no pleat break | Dedicated wave track | No |
| Eyelet | The UK word for grommet | See grommet | Rod | Yes, as grommet |
Wave header curtains are the ripple-fold heading above: a continuous S-shaped wave rather than discrete pleats, created by a carrier tape on a matching track. The look depends on the track, so wave panels are not interchangeable with rod curtains.
Header tape / heading tape. A stiffened strip sewn across the top of a panel with woven pockets and draw cords; pulling the cords forms pleats and the pockets take hooks. Grommet and back-tab panels do not use it.
Heading allowance. The vertical distance between the very top of the fabric and the top of the rod opening. It is why a grommet panel hangs a little lower than the rod, and why "length" is measured from the fabric top, not from the rod.
Curtains that use hooks. Pleated and taped headings (pinch, pencil, goblet) hang on hooks. Grommet, back-tab, tab-top and rod-pocket panels do not need hooks at all.
More on choosing between tops: curtain heading types and grommet vs rod pocket vs back tab.
Opacity and lining
Opacity words describe the fabric. The darkness of your room also depends on gaps at the top, the sides and the middle, so no fabric grade alone promises a dark room.
Blackout. Blackout describes fabric engineered to stop essentially all light passing through the cloth itself, usually with a dense weave, a coated layer, or a bonded liner. Light still enters around the panel, at the top, sides and center overlap.
100% blackout. A fabric-level claim about light passing through the material. It is not a claim about the room. Ona's grommet pair, wide panel and back-tab pair use supplier-listed 100% blackout fabric; that is the supplier's specification, not an Ona measurement, and light can still enter at the top, the sides and the center.
Light blocking curtains. A marketing synonym for blackout or near-blackout. It carries no standard, so read the lining description instead.
Room darkening. A grade below blackout: the fabric cuts most light and glare but leaves a visible glow. Ona's velvet pair is room-darkening and unlined — not blackout.
Non-blackout / non blackout curtains meaning. Any curtain whose fabric is not built to stop light: sheer, light filtering or plain unlined cloth. The room still gets noticeably darker, just not dark.
Light filtering. Fabric that diffuses daylight while keeping the room bright and giving daytime privacy. Ona lists no light-filtering product.
Sheer. A thin, semi-transparent fabric such as voile that softens light and gives almost no privacy after dark. Ona's sheer is a coming-soon preview with no size, price or opacity details.
Lining. Lining is a second layer of fabric attached behind the face fabric. It blocks light, protects the face fabric from sun, improves how the folds hang, and adds a little insulation.
Curtain lining, what curtains are lined with. Ready-made panels are usually lined with a woven polyester, sometimes with a coated or foam-backed blackout finish; made-to-measure curtains may use cotton sateen. Ona lists the grommet pair, wide panel and back-tab pair as lined (the back-tab pair has a dedicated liner per the supplier) and the velvet pair as unlined.
Interlining. A soft third layer sandwiched between face fabric and lining, used in made-to-measure drapery for body, light control and insulation. Ready-made panels, including Ona's, are not interlined.
Thermal. Thermal describes a lining or backing intended to slow heat moving through the window. There is no consumer standard and no rating on ready-made panels. All four Ona styles are listed by the supplier as thermal insulating; no insulation rating is published, and no energy saving is claimed.
Triple weave. A three-layer woven construction, marketed as achieving opacity without a coating. It is a weave description, not a certified opacity grade.
Blockout. The UK and Australian spelling of blackout.
Compare the grades side by side in blackout vs room darkening curtains, or browse blackout curtains.
Size and fit
Flat width. The width of one panel laid flat and unpleated. It is the number on the listing. Gathered on a rod, a panel covers roughly a third to a half of its flat width.
Fullness. Fullness is the ratio of total flat fabric to rod width. Fullness = total flat fabric ÷ rod width. 1.5× looks light, 2× is the standard target, 2.5–3× looks luxurious, and 1× looks flat and skimped.
Drop (UK) / length (US). The finished vertical measurement from the top of the fabric to the bottom of the hem. "Curtain drops" means the same thing in the plural, and is often how UK listings label stock sizes.
Return. The return is the short stretch of fabric at each end that wraps from the face of the curtain back to the wall, closing the side gap. Its depth equals your bracket's projection — typically a few inches. Grommet panels return poorly because the ring nearest the end has to sit on the rod.
Center overlap. The amount the two leading edges cross in the middle when closed. Aim for 2–4″ so no slit of light runs down the middle.
Stack back. The width your panels occupy when pushed fully open, measured on the wall each side of the window. The fuller the curtain, the bigger the stack. If you want all the glass clear, your rod must be long enough for the stack to sit beyond the frame.
Rod width. Measure your rod end to end without the finials, because fabric cannot travel over a finial. Plan the rod 6–12″ past each side of the window frame; Ona's examples use 8″ a side.
Float. A hem that stops about ½″ above the floor. Order length = floor-to-fabric-top − ½″. It is the easiest finish to keep clean and is forgiving of uneven floors.
Floor kiss. A hem that just touches the floor. Order length = floor-to-fabric-top, exactly. It looks tailored and leaves no room for error.
Puddle. A hem that pools on the floor. Order length = floor-to-fabric-top + 4″ for a light puddle. Ona treats puddle as +4″.
Break. The small fold a hem makes where it meets the floor on a kiss or puddle finish.
Sill length / apron length. Finishes that stop at the window sill, or a few inches below it on the apron. Ona's shortest panel is 63″, which on a standard window hung just above the frame lands below the sill rather than on the floor; it only reaches the floor where the rod sits about 63″ up.
Extra long curtains / long curtains. Panels longer than the common 84″ and 96″ stock sizes — 108″ and 120″ — for high ceilings or rods hung near the ceiling line.
XL curtains. A label with no fixed meaning: sometimes extra wide, sometimes extra long. Check the actual inches.
Extra wide curtains. Panels wider than the standard ~50″, so one panel covers more rod. Ona's wide panel is 70″ flat.
What "52 × 84" means. Width first, then length, in inches, per panel. A pair listed 52 × 84 is two panels, each 52″ wide and 84″ long.
Hem. The folded and stitched bottom edge. A deep hem adds weight so the panel hangs straight.
Curtain weights. Small flat weights sewn into the bottom hem or corners to keep the panel hanging plumb. They are part of the panel, not an accessory you buy.
Coverage. What the closed panels actually hide: rod width plus return, minus any gap. Coverage, not panel width, is what makes a room dark.
Full worked examples: how wide should curtains be, how many curtain panels do I need and the curtain size chart.
Hardware
Ona sells panels only — no rods, rings, hooks or tracks — so these entries are here to help you read other people's listings.
Curtain rod / pole. A round rail, usually metal or wood, held on brackets, that panels hang from. Diameter matters for grommets: the rod must pass through the ring.
1″ vs ¾″ rod. A 1″ diameter rod is stiffer and spans wider windows with less sag; a ¾″ rod is lighter, cheaper and better suited to short spans and light panels. For grommet panels, the ring's inside diameter must clear the rod — typically 1½–1⅝″ rings take a 1″ rod comfortably.
Finial. The decorative end cap screwed onto each end of a rod. It stops rings sliding off, and it is excluded when you measure rod width.
Bracket. The wall or ceiling fixing that holds the rod. Its projection sets how far the rod sits off the wall, and therefore your return depth.
Center bracket / center support. An extra bracket mid-span on a long rod. Panels cannot slide past it, so plan which panels live on each side.
Curtain rail / track. A flat or channel-shaped rail, often plastic or aluminum, in which gliders run. Tracks suit pleated, taped and wave headings and can be ceiling mounted or bent around a bay.
U rail. A U-shaped profile track, common in UK and multi-family installations, taking gliders or hooks.
Gliders / runners. Small plastic carriers that slide inside a track and accept curtain hooks.
Curtain rings. Rings that slide along a rod, each with a small eye underneath for a hook or clip. They let pleated or flat panels move freely.
Curtain hooks. Small hooks that connect a heading to rings or gliders. Flat pin hooks push into a pleat or tape pocket; standard hooks slot into tape pockets.
Curtain clips. Small clips, usually on rings, that grip the top edge of a panel. They turn almost any flat panel into a hanging curtain and raise the fabric top above the rod.
Tieback. A fabric or cord band that gathers an open panel to one side.
Holdback. A rigid hook or arm fixed to the wall that holds a panel open without a band.
Baton / wand. A slim rod clipped to the leading edge so you can draw curtains by hand without touching the fabric.
Valance. A short fabric strip across the top of a window that hides the hardware.
Pelmet. The UK term for a rigid or stiffened covered box above the window that conceals the rod or track. "Pelmet curtains" means curtains fitted behind one.
Cornice. The US equivalent of a pelmet: a hard, usually upholstered box top treatment.
Roman blind / "roman curtains". Not a curtain. A flat fabric shade that draws upward into horizontal folds on cords. Ona does not sell blinds or shades.
Fabric and weave words
These describe appearance and construction. Fiber content is only ever what a specification sheet states, so check each listing.
Jacquard. Jacquard curtains have a pattern woven into the cloth on a jacquard loom rather than printed on top, so the design shows in the weave and often reverses on the back.
Chenille. Chenille curtains use a fuzzy, caterpillar-like yarn that gives a soft pile and a subtle sheen. It drapes heavily and shows pressure marks.
Bouclé. Bouclé curtains use a looped yarn that creates a nubbly, textured surface. The texture comes from the yarn's loops, not from a print.
Velvet. A woven pile fabric with a short, dense, upright nap, so it reads darker or lighter depending on viewing angle. Ona's velvet pair is listed by the supplier as 100% polyester, unlined and room darkening.
Linen look / faux linen. A description of appearance only: a slubby, open-looking texture made to resemble linen. It says nothing about fiber. Ona uses "linen texture" and "linen-look" for appearance; "Linen" also appears as a color name.
Slub. Thick-and-thin irregularities in the yarn that create a visible linen-like texture.
Weave. How warp and weft interlace. A denser weave passes less light and hangs with more weight.
Solid. One color across the panel, no pattern. Every Ona panel is solid.
GSM. Grams per square meter, a fabric weight measure. A GSM figure without a unit is meaningless, so Ona publishes none.
Glass curtains. Two unrelated meanings: in architecture, a non-structural glass façade (a curtain wall); in soft furnishings, very lightweight sheers hung close to the glass.
What curtains are made of. Most ready-made panels are polyester or polyester blends, sometimes cotton, linen or viscose; blackout panels add a coated or bonded liner. Ona states fiber only where the supplier's specification does — 100% polyester for the velvet pair, and nothing for the grommet or back-tab fabrics.
Other meanings of "curtain"
The word travels well beyond windows. These show up in the same searches, so here they are, briefly.
Curtain up / curtain call / curtain raiser. Theater terms: curtain up is the start of a performance, a curtain call is the cast's final bow, and a curtain raiser is a short opening act — now used for any warm-up event.
Kabuki curtain / kabuki drop. A stage curtain rigged to drop instantly on cue, used for reveals.
Noren. A short Japanese fabric divider hung in a doorway, split vertically, traditionally marking a shop entrance.
Curtain divider / room divider curtain. A panel on a track or wire used to split a space rather than cover a window.
Bed curtains. Fabric hung from a canopy or frame around a bed, historically for warmth and privacy, today mostly decorative or for light control.
Curtain-side trailer / curtainsider. A truck trailer whose sides are tensioned fabric that slides back for loading from the side.
Curtain wall. A building's non-load-bearing outer skin, usually glass and aluminum.
Iron Curtain / Nylon Curtain. Political metaphors for a hard political division; the second is a journalistic coinage echoing the first.
A curtain across your vision. Not a window term. A dark curtain, shade or veil moving across your field of vision is a medical symptom, not a decorating one — seek urgent eye care rather than a glossary.
When were curtains invented? Fabric window and doorway hangings are ancient, documented in Egyptian, Greek and Roman interiors long before glazed windows were common; curtains as a standard household furnishing in the Western home followed cheap woven cloth and plate glass. Blackout curtains entered mass use as wartime civil-defense blackout material in the first half of the twentieth century.
Why curtains are used. Five jobs, in rough order of how often people buy for them: light control, privacy, sleep, temperature and noise comfort, and finishing the look of a room. A panel wide enough to close with fabric to spare does all five better than a narrow one.
How Ona uses these words
Ona sells four ready-made styles, solid colors only, in US sizes, with no custom sizing and no hardware. Every width and length below is the flat size of one panel.
| Style | Sold as | Flat width per panel | Lengths | Heading | Lining | Opacity wording | From |
|---|---|---|---|---|---|---|---|
| Linen Texture Grommet Pair | 1 pair · 2 panels | 42″ or 52″ | 63–96″ (42″ wide) · 63–108″ (52″ wide) | Metal grommets | Lined | Supplier-listed 100% blackout fabric | $189 / pair |
| Wide Grommet Panel | 1 single panel | 70″ | 90, 96, 108″ | Metal grommets | Lined | Supplier-listed 100% blackout fabric | $139 / panel |
| Back-Tab & Rod-Pocket Pair | 1 pair · 2 panels | 52″ | 63–120″ | Hidden back tabs and rod pocket | Lined (dedicated liner, per supplier) | Supplier-listed 100% blackout fabric | $189 / pair |
| Velvet Grommet Pair | 1 pair · 2 panels | 52″ | 63–108″ (selected colors per length) | Metal grommets | Unlined | Room darkening, not blackout | $139 / pair |
Prices are the live "from" figures as of 16 October 2026 and can change; the product page is always right. All four styles are listed by the supplier as thermal insulating, with no insulation rating published. Ona has not sampled or tested any fabric, so opacity and thermal wording is the supplier's, not a measurement.
Words Ona does not use about its own panels: linen as a fiber (only as a color name and as "linen texture"), light filtering, motorized, sheer and pinch pleat as sellable products, or any percentage of light or heat blocked.
Room images on Ona are AI styling visualizations, not proof of color, size or opacity.
Glossary of the offer
Item. The offer counts items, not panels. A pair of two panels counts as one item. A single wide panel counts as one item.
Buy 2, get 1 free. For every three eligible items in the cart, the lowest-priced one is free. It repeats: six items make two free.
Bonus 20% off 4+. At four or more eligible items, a further 20% comes off the order.
Stacking. Both discounts apply together, automatically, at the cart. At four pairs of the $189 grommet pair, that is $453.60.
Compare-at price. The struck-through figure next to the selling price, about 30% above it — for example $249 struck through, selling at $189.
| Order | Panels | Items | What applies |
|---|---|---|---|
| 1 pair | 2 | 1 | No discount yet |
| 2 pairs | 4 | 2 | No discount yet |
| 3 pairs | 6 | 3 | Buy 2 get 1 free: lowest-priced pair free |
| 4 pairs | 8 | 4 | Lowest-priced pair free plus 20% off the order |
| 3 wide panels | 3 | 3 | Buy 2 get 1 free: lowest-priced panel free |
All four styles are eligible, and you can mix styles, colors and sizes. Free US shipping; orders arrive in about 10–14 days. Returns are accepted for damaged, defective or incorrect items only. Full terms: curtain offers and the refund policy.
Ready to use the words?
Measure your rod end to end without the finials, double it, and divide by the flat width of one panel. Then pick your hem finish: float, kiss or puddle.
Shop all curtains → — four styles, 42″, 52″ and 70″ flat widths, 63″ to 120″ long, solid colors, grommet or back tab. Or jump straight to blackout curtains, grommet curtains, back-tab curtains or velvet curtains.
Not sure of your size yet? The curtain calculator turns a rod width into a panel size and a panel count.
Curtain term questions, answered
What does 2 panels mean when buying curtains?
It means you receive two curtains, one for each side of the window, and the listed width is the flat width of each panel. A pair listed 52″ wide is two 52″ panels, or 104″ of flat fabric, which suits a 52″ rod at 2× fullness.
What is a single curtain panel?
One curtain sold on its own, rather than as a pair. Use one where a narrow window needs a single side, where a door draws one way, or where an odd number of panels covers a wide run. Ona's single is a 70″ wide grommet panel.
What are curtain eyelets?
Eyelet is the UK word for grommet: metal-rimmed rings punched through the top hem, with the rod passing directly through them. They give deep, even waves and slide easily, and the rod must be narrower than the ring opening.
What is curtain lining?
Lining is a second fabric layer attached behind the face fabric. It blocks light, shields the face fabric from sun, helps the folds hang, and adds a little insulation. Ona's grommet pair, wide panel and back-tab pair are lined; the velvet pair is unlined.
What does blackout mean on curtains?
It describes fabric built to stop essentially all light passing through the cloth itself — not a promise about your room, since light still enters at the top, the sides and the center overlap. Ona's grommet pair, wide panel and back-tab pair use supplier-listed 100% blackout fabric.
What is the difference between blackout and room darkening?
Room darkening is the lighter grade: it cuts most light and glare but leaves a visible glow, and the panel is often unlined. Blackout fabric stops essentially all light through the cloth. Ona's velvet pair is room darkening and unlined, not blackout.
What is a curtain return?
The return is the few inches of fabric at each end that wrap from the front of the curtain back to the wall, closing the side gap. Its depth equals your bracket's projection.
What are wave header curtains?
Panels made for a ripple-fold or S-fold system: a carrier tape on a dedicated track holds the fabric in one continuous wave instead of separate pleats. They need that track, so they are not interchangeable with rod curtains.
What are jacquard curtains?
Curtains with the pattern woven into the fabric on a jacquard loom rather than printed on the surface, so the design appears in the weave and often reverses on the back.
What is the difference between drapes and curtains?
In US usage drapes are heavier, lined, often pleated and usually floor length, while curtains are lighter, often unlined and sold in ready-made sizes. The terms overlap and neither implies a specific size or opacity.
What is the rule of thumb for curtains?
Rod 6–12″ past each side of the window, total flat fabric about twice the rod width, length measured from the top of the fabric to the hem, and a hem that floats ½″ above the floor, kisses it, or puddles 4″ onto it.
How many types of curtains are there?
There is no fixed number, because curtains are classified four ways at once: by heading (grommet, back tab, tab top, rod pocket, pinch pleat, pencil pleat, wave), by opacity (sheer, light filtering, room darkening, blackout), by construction (unlined, lined, interlined) and by length. Ona covers grommet and hidden back tab (the back-tab pair doubles as a rod pocket), two opacity grades, and lengths from 63″ to 120″. See types of curtains.
What is the difference between a 1-inch and a 3/4-inch curtain rod?
A 1″ rod is stiffer, so it spans a wider window with less sag and carries heavier lined panels; a ¾″ rod is lighter and cheaper and suits short spans. With grommet panels, check that the ring's inside diameter clears the rod before buying either.