To order the right leg cap or ferrule, you need one number: the diameter of the leg end. Measure the outside diameter if the cap slips over the leg, or the inside diameter if the ferrule pushes into a hollow leg. Round legs use round caps; square legs use square caps; tapered legs need tapered hardware. Bespora stocks round open-end ferrules in 34 sizes, round leg caps in 37 sizes, and tapered and square options too, so matching your measurement is usually straightforward.
How to Measure in 5 Steps
- Identify the leg shape — round, square, or tapered. Square legs need square caps (e.g. square leg caps); round legs need round caps; tapered legs need tapered hardware (e.g. tapered leg caps).
- Decide cap type — a cap covers the end from outside (for solid legs); an open-end ferrule inserts into a hollow leg (e.g. round open-end ferrules).
- Measure diameter — use calipers for best accuracy, or a ruler across the leg end. Measure the dimension the hardware will grip.
- Match to size chart — compare your mm measurement to the product size chart; when between sizes, the cap should fit snug, not loose.
- Check depth — for open-end ferrules, note how deep the leg wall is so the ferrule seats fully.
Round, Square, or Tapered?
The shape of the leg decides the shape of the hardware — there is no universal cap.
- Round legs take round caps or round ferrules. Measure the leg’s outside diameter. See round leg caps (closed base) or round open-end ferrules.
- Square legs need square hardware — never force a round cap onto a square leg. Measure the flat-to-flat distance. See square open-bottom ferrules or square closed-bottom foot cups.
- Tapered legs (common on mid-century and cane / walking-stick furniture) narrow toward the end. You need tapered hardware that follows the cone. Measure the diameter at the depth where the cap will sit. See tapered leg caps or tapered open-end ferrules.
Closed-Base Cap vs Open-End Ferrule
This is the one decision that changes everything else:
- Closed-base cap (e.g. round leg caps, closed-end foot cups) has a solid bottom. It caps the end of a solid leg, seals the wood from moisture, and sits on the floor as a foot. Choose this when the leg is solid or when you want a finished floor-protector foot.
- Open-end ferrule (e.g. round open-end ferrules, tapered ferrules) is a sleeve open at both ends. It slides onto the end of a leg (solid or hollow) and grips the outside, or into a hollow leg to reinforce a thin wall. Choose this when you want to collar the leg without covering the end, or to strengthen a tubular leg.
OD vs ID — The Diameter That Actually Matters
Two diameters come up, and mixing them up is the most common sizing mistake:
- Outside diameter (OD) — the widest part of the leg. Caps that slip over the leg are matched to the leg’s OD.
- Inside diameter (ID) — the bore of a hollow leg. Ferrules that push into a hollow leg are matched to that bore’s ID.
Our open-end ferrules list the leg diameter they accept as the ID, and each has a 1.5 mm wall. If you ever need the ferrule’s outer diameter from the inside, the relationship is simple:
ID = OD − 2 × wall → so a ferrule’s outer diameter = its listed ID + 3 mm (1.5 mm on each side).
In practice: measure the leg’s OD (or the hollow bore’s ID) and pick the matching listed size. When you are between two sizes, the hardware should be snug, not loose — a loose cap falls off and an over-tight one can crack a thin leg.
Common Size Reference
| Product | Type | Size range |
|---|---|---|
| Round leg caps | Closed base (slips over solid leg) | 18–60 mm, 37 sizes |
| Round open-end ferrules | Open sleeve (into hollow leg) | Ø14–77 mm ID, 34 sizes |
| Square leg caps | Open-bottom ferrule | 25–60 mm, 24 sizes |
| Square foot cups | Closed bottom (floor foot) | 34–48 mm, 3 sizes |
| Tapered leg caps | Closed base, cone shape | 15 sizes |
| Tapered ferrules | Open sleeve, cone shape | Top OD 28–55 mm, 15 sizes |
| Closed-end foot cup | Floor-seating cap for legs & armrests | Custom sizes |
Hollow Legs
Many chairs and stools have thin-wall tubular legs. An open-end ferrule expands slightly to grip the inner wall, which is why the inside diameter is the number to capture. If your leg is solid, measure the outside diameter instead and choose a cap that slips over the end.
Solid Brass or Plated?
Before you buy, confirm the hardware is solid brass and not a brass-colored coating that flakes within a year. Quick checks:
- Magnet test: solid brass is not magnetic. If a magnet sticks, the core is steel — it’s plated, not solid.
- Weight: solid brass is noticeably heavier than zinc or steel of the same size.
- Cut edges: at a screw hole or cut, solid brass shows a uniform golden color; plating shows a different-colored core.
Every Bespora leg cap and ferrule is machined from one solid brass bar — never plated. For the full material comparison, see our solid brass vs plated guide and complete brass hardware guide.
Frequently Asked Questions
What is the difference between a leg cap and a ferrule?
A cap has a closed (or open) base that covers the leg end; a ferrule is an open sleeve that collars the leg. Closed-base caps also act as floor feet, while open-end ferrules reinforce or finish a leg without covering its end.
How do I know if my leg is tapered?
A tapered leg narrows toward the floor. Hold a ruler across the leg at two different heights — if the diameter changes, it’s tapered and you need tapered hardware measured at the depth where the cap will sit.
Should a leg cap fit tight or loose?
Snug. A loose cap falls off; an over-tight cap can crack a thin or hollow leg. When between sizes, choose the size the leg grips without force.
Is Bespora’s brass solid or plated?
Solid. Every piece is machined from a solid brass bar and never plated, so it can be re-polished for generations rather than flaking.
Still deciding on material or finish? Our brass vs aluminum guide and brass vs steel comparison cover the trade-offs, and the complete brass hardware guide explains every part type and finish.