Odd lug widths are a manufacturing decision that becomes the owner's problem. The strap industry standardised on even numbers — 18, 20, 22, 24mm — because stocking every width in every colour and material doubles the catalogue. Watch brands did not get that memo. Orient fits 21mm lugs to the Bambino and the Bambino Sun & Moon, Citizen has used 19mm and 21mm for decades, and a lot of vintage cases are 19mm. The result is a watch you like and a strap drawer that does not fit it.
This page is short on purpose. There are four straps in our registry made in odd widths, and padding the list with even-width straps that do not fit would defeat the point. If you want the full even-width rankings instead, they are on 20mm, 22mm, 18mm and 24mm.
Measure before you buy anything
21mm is a number people guess at and get wrong, usually by assuming a 41mm watch must be 22mm. Measure the gap between the inside faces of the lugs with digital calipers, or with a ruler if that is what you have — the method and a brand-by-brand table are on the watch lug width chart, and the measuring technique is on how to measure a watch strap.
A 21mm measurement is almost always genuinely 21mm rather than a mis-measured 20 or 22, because manufacturers who go to the trouble of an odd width do it deliberately. The Orient Bambino V2 and the Bambino Sun & Moon in our registry are both 21mm, and both list it as such.
How this page is ranked
Whether the odd width is actually stocked first. Three of the four picks here state 19, 21 or 23mm availability in their own listings. That is the whole qualification, and it is why a better strap that stops at even widths is not on this page.
Then material and comfort, because with the width question settled you are choosing the same way everyone else does. Then hardware: quick-release bars matter more on an odd width, because replacing a strap you had to hunt for is a job you want to do without a tool — the mechanism is explained on the quick-release roundup. Then price, which on odd widths is usually a small premium.
The four options, and what each solves
Archer Soft Silicone is the one we would buy first. It is listed from 16mm to 24mm including 19 and 21mm, the compound is the softest rubber in our registry, and it is waterproof — so a 21mm dress watch with a 30m rating gets a strap you can at least rinse. Its limitation is tone: every rubber strap reads sporty, which on a Bambino is a deliberate look rather than an accident.
Barton Canvas Quick-Release is the field answer, listed in 19, 21 and 23mm with a brushed 316L stainless buckle and machine-washable canvas. It is stiff for the first week and it is not a swimming strap, but on a 21mm case it looks correct in a way nylon does not.
Ritche Quick-Release Leather is the cheapest leather that covers 19, 21 and 23mm, with quick-release bars at a price where most leather straps still use plain spring bars. The leather is thin and takes a while to soften; treat it as a consumable rather than an heirloom.
Clockwork Synergy Croco-Grain Leather is here for range: its listed widths run from 12mm to 28mm, the widest span of any strap in our registry, which makes it the first place to look when the width you need is out of stock everywhere else. The croco embossing is a print, and it looks like one up close.
What to do when 21mm is unavailable
Three honest options, in order of how well they work.
Fit a 20mm strap. A 1mm gap either side is visible if you look for it and invisible to everyone else, and the strap will seat on the spring bars perfectly well. This is what most owners of 21mm watches actually do, and on a dark strap against a steel case it genuinely disappears.
Do not force a 22mm strap. It will not go in without compressing the strap end, and the pressure works against the lugs and the spring bar every time you move. A strap that has to be squeezed into place is a strap that will mark the inside of the lugs.
Consider a pass-through NATO. A single-pass nylon strap in 20mm sits under the case rather than between the lugs, so the width mismatch shows even less — and a NATO keeps the watch on your wrist if a spring bar fails. The rankings are on the best NATO straps, and the construction differences are on NATO vs Zulu.
19mm and 23mm, while you are here
The same four brands cover them. Barton's canvas and Ritche's leather both list 19 and 23mm; Archer's silicone lists 19mm; Clockwork Synergy's range spans 12mm to 28mm. 19mm turns up on older Citizens and a great deal of vintage, and 23mm is rare enough that it is usually a chronograph. In both cases the rule from 21mm applies: going 1mm narrower is fine, going 1mm wider is not.
The spring bar question
A 21mm strap needs a 21mm spring bar, and odd-width bars are harder to find than odd-width straps. Every quick-release strap on this page ships with its own bars, which sidesteps the problem entirely — one more reason quick-release matters more at odd widths than at 20mm. If you are fitting a strap that does not include them, the sizing rules are on the watch spring bar size guide.
What we would buy
One 21mm strap for a Bambino: the Archer silicone for comfort, or the Ritche leather if the watch has to stay dressy. A 21mm field or casual look: the Barton canvas. An unusual width or colour nobody else stocks: Clockwork Synergy. 21mm unavailable and you need it today: a 20mm strap, and nobody will notice.
