Sizing

Find your size in 2 minutes

Your cap size is the inside diameter of the chair tube, measured across the opening where the old cap sat. Most camp chairs fall in the 8–13 mm range.

First page of the printable pole size gauge, showing the scale-check box, circle gauges and ruler

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Measure this, not that

Inside diameter, not outside

The cap presses into the tube, so the number that matters is the opening, not the outside. Measuring the outside will send you a size too large.

Three methods

Pick whichever you have to hand

Any of these gets you to the right size. The printable guide is the most accurate if you have no calipers to hand.

Digital calipers held in both hands with the inside jaws seated in the end of a black chair tube, the display reading 11.70 in millimetre mode — A real tube, measured: 11.70 mm. Round down — this one takes the 11 mm cap.

Method 1

Calipers or a ruler

Measure straight across the inside of the tube opening, through the center, to the nearest 0.5 mm. That measurement is your cap size.

A black end cap stood upright on the millimetre ruler printed on an M-LAB pack, its body spanning the scale from zero

Method 2

The pack in your hand

The topper carries an actual-size 25 mm ruler. Lay your old cap along it and read the body — the end that was inside the tube — not the wider head. The four caps are visible through the bag, so you can hold yours against them as well.

Two black M-LAB end caps on a printed sheet, the right one resting exactly on the actual-size outline labelled 11 mm — Printed at 100%, a real cap lands on its outline.

Method 3

The printable guide

Print the free guide at 100%. A circle gauge, a ruler, a cut-out taper strip, and actual-size outlines to lay your old cap on.

Printing instructions →

Size chart

All 8 sizes, drawn to scale

Head diameter is always 4 mm larger than the tube bore, so the cap seats against the tube end instead of dropping in.

All dimensions in mm · Every cap is 27.5 mm long · Pack of 4 · Between two sizes, choose the smaller — the bungee is what holds the cap in.

Cap size, pole inside diameter, head diameter and SKU for all 8 sizes
Size	Pole inside Ø	Head Ø	SKU	Buy
08	8 mm	12 mm	MLAB-EC-08MM-4PK	Select 8 mm
09	9 mm	13 mm	MLAB-EC-09MM-4PK	Select 9 mm
10	10 mm	14 mm	MLAB-EC-10MM-4PK	Select 10 mm
11	11 mm	15 mm	MLAB-EC-11MM-4PK	Select 11 mm
12	12 mm	16 mm	MLAB-EC-12MM-4PK	Select 12 mm
13	13 mm	17 mm	MLAB-EC-13MM-4PK	Select 13 mm
14	14 mm	18 mm	MLAB-EC-14MM-4PK	Select 14 mm
15	15 mm	19 mm	MLAB-EC-15MM-4PK	Select 15 mm

Your measurement will not be exact

Tube sizes vary between makes, and a tube that has been in use is usually a little out of round. In our testing a reading almost never matches a size exactly — the tube in the calipers above came out at 11.70 mm, not a clean 11.

Round down to the nearest size we make. That 11.70 mm reading takes the 11 mm cap. A little under is fine: the head is 4 mm wider than the bore, so it still seats on the tube end, and the bungee is what holds the cap in. Go too far under and the head pulls straight through instead of seating.

Calipers read in inches?

Round your reading to three decimals, then find it in the left column. The rows are exact at that precision — every thousandth from 0.315″ to 0.629″ lands in exactly one row, and that row is the size the round-down rule gives you.

Inch reading ranges and the cap size each one takes, for all 8 sizes
Your reading	Take
0.315″ – 0.354″	08 mm
0.355″ – 0.393″	09 mm
0.394″ – 0.433″	10 mm
0.434″ – 0.472″	11 mm
0.473″ – 0.511″	12 mm
0.512″ – 0.551″	13 mm
0.552″ – 0.590″	14 mm
0.591″ – 0.629″	15 mm

Common fractional tube sizes: 5/16″ under our range · 3/8″ takes 9 mm · 7/16″ takes 11 mm · 1/2″ takes 12 mm · 9/16″ takes 14 mm · 5/8″ takes 15 mm.

Measured under 0.315″ or over 0.629″? Ask us for that size — we make them to order.

Where it goes

The cap fits the open end of the tube

A folding camp chair frame upside down on a wood floor, with an arrow marking the open end of a leg pole where the end cap fits — The cap goes in the open end of the tube, where the bungee comes through.

Caps sit in the open end of each leg or frame tube, where the shock cord passes through. Pull the broken cap out first, then measure the opening it came from.

Caps are sold in packs of 4. You usually only need one — the rest are spares for next time.

Still stuck? Print the measuring guide — the actual-size outlines settle it.