What size strap fits the Isotope GMT 0?

24mm at the lugs, tapering to 22mm. The basis is the GMT 0 product page's own spec line 24mm strap tapered to 22mm plus the brand's Tan Suede 24/20mm strap page, which says the strap is designed to fit all watches with a 24mm lug size (the Isotope GMT 0, for example). The GMT 0 page never prints the words lug width, so the 24mm rides on those two first-party sentences instead.

Will a 20mm strap fit an Isotope Hydrium?

No. Every Hydrium variant in the brand's feed, base Hydrium, Hydrium X and Hydrium Pro alike, prints 22mm: stock FKM straps are 22/20mm quick-release, the Hydrium S.S. Bracelet tapers from 22 mm to 18 mm, and the brand's own Tan Suede 22/20mm strap page says it fits all watches with a 22mm lug size.

What strap width is the Isotope Moonshot chronograph?

20mm at the lugs, tapering to 18mm. Both factory options print it: the titanium bracelet is listed as tapered from 20mm to 18mm, and the FKM Cut-to-Size straps measure 20mm at the lugs and taper to 18mm with a quick-release system. The matching Moonshot Butterfly Buckle is the 18mm clasp end.

Do Isotope watches use quick-release straps?

Yes, across the catalog. Every strap line quoted in this chart carries the words quick-release: FKM, suede, calfskin, Cordura and the steel bracelets on the Flyway, Moonshot and GMT 0 all ship with quick-release spring bars or buttons.

Isotope band size chart: the whole catalog on 18, 20 and 22mm, plus the one 24mm outlier

Isotope is the micro brand whose Lacrima teardrop hands and i-logo buckles show up in every family photo, from the square OVNI jumping discs to the 300m Hydrium divers. Its strap widths are easy to read once you know where the brand hides them: inside the Strap and Bracelet lines of the product copy in the isotopewatches.com merchant feed, 129 products on one page, page two empty ^[23]^[24]. This chart tables those lines word for word, family by family, and refuses to invent the few that stay silent.

The width rail, family by family

Four widths cover the whole watch catalog. The numbers below come only from the brand's own Strap:, Bracelet: and quick-release lines, never from case dimensions, and each row quotes the feed exactly as printed.

Family	Lug width	Feed line, verbatim	Source
Flyway, every variant	18mm	Bracelet: 18mm quick-release 316L stainless steel bracelet with a signed butterfly clasp.	[4]
Mercury	20mm	Strap: 20mm Quick-release Cream Suede leather strap with signed brushed Dark Gold Stainless Steel Buckle (included)	[6] [7]
Old Radium bronze watches	20mm	20mm Quick-release Suede Italian strap with bespoke Bronze Brushed Buckle	[22]
OVNI Jumping Disc	20mm at lugs, 18mm at clasp	Strap: Orange 20/18mm quick-release FKM rubber with Isotope-branded spring-loaded clasp	[1] [2] [3]
Moonshot chronograph, bracelet	20mm tapering to 18mm	Sandblasted Titanium Grade 5, signed butterfly buckle, Quick Release, screwed links, tapered from 20mm to 18mm	[12]
Moonshot FKM Cut-to-Size straps	20mm at lugs, 18mm taper	Measuring 20mm at the lugs and tapering to 18mm, it features a quick-release system for easy changes.	[13]
Hydrium, base divers	22mm (stock straps 22/20)	Strap: 22/20mm quick-release grey FKM with Isotope-branded bead-blasted stainless steel buckle	[5] [8]
Hydrium X	22mm	22mm Quick-release light blue FKM strap with signed Stainless Steel buckle.	[9]
Hydrium Pro	22mm	22mm Quick-release black FKM strap with a micro-blasted Steel Buckle	[10] [11]
Goutte d'Eau Compressor Diver	22mm bracelet	22 mm brushed Isotope Tread Bracelet and extension clasp in 316L stainless steel	[20]
Rider Jumping Hour	22mm	Lugs width: 22 mm	[19]
GMT 0	24mm tapering to 22mm	24mm strap tapered to 22mm	[14] [15]

The GMT 0 basis, stated plainly

The GMT 0 is the only Isotope that leaves the 18/20/22 system, and it is also the one watch whose width the brand never labels lug width. The 24mm rests on two first-party sentences: the GMT 0 product page's own specification block prints 24mm strap tapered to 22mm ^[14], and the brand's Tan Suede 24/20mm strap page prints the strap is designed to fit all watches with a 24mm lug size (the Isotope GMT 0º, for example) ^[15]. A fitting sentence on a strap product, not a watch spec line, is the rail here; that is the disclosure, and it is why the row carries two sources instead of one.

The strap shop corroborates the rail

Isotope sells its own straps, and the fitting sentences on those pages independently confirm the watch-side numbers. The suede and leather pages map one to one onto the watch families:

Strap product	Fits, per the brand	Fitting sentence, verbatim	Source
Tan Suede 24/20mm	24mm lug size	the strap is designed to fit all watches with a 24mm lug size (the Isotope GMT 0º, for example)	[15]
Tan Suede 22/20mm	22mm lug size	the strap is designed to fit all watches with a 22mm lug size.	[17]
Grey Suede Round 20/18mm	20mm lug width	the strap is designed to fit Mercury or Bronze Watch cases with a 20mm lug width	[16]
Mercury S.S. Bracelet	20 mm tapering to 18	Tapering from 20 mm to 18 mm	[18]
Hydrium S.S. Bracelet	22 mm tapering to 18	Tapering from 22 mm to 18 mm	[21]

The trap: lug-to-lug is not a strap width

Isotope product copy is full of numbers ending in mm that are not strap widths: the Flyway page prints 36mm diameter × 12.3mm thickness / 42mm lug-to-lug ^[4], the Hydrium divers print 40mm × 48mm (including lugs), the OVNI prints 40 × 40mm (including lugs). Those are case and length-over-lugs measurements. A 42 or 48 read off those lines is the classic wrong answer, and this rail was built to exclude them: only Strap:, Bracelet:, quick-release and explicit lug-size wording above was allowed to set a width. The nearest-number instinct is exactly how 20mm Hydrium charts get published.

Not printed, not guessed

A few rows in the 129-product feed ship straps with no width anywhere in the copy: the Palloncino di Perle (quick-release leather strap with signed butterfly clasp, no number), the Cool Hunting GMT 0 Limited Edition (mentions its extra Quick-Release leather strap, no width), the 4L'MENTS Goutte d'Eau strap collaboration (no width), and the GMT 0 and Goutte d'Eau stainless bracelet product pages, which promise perfect fit for their own watches but print no millimeters. Those stay flagged rather than backfilled. The Goutte d'Eau watch row above is saved by its own Tread Bracelet spec line at 22 mm ^[20]; the bracelet accessory page alone would not have carried it.

Buying notes

Three practical consequences fall out of the rail. First, the OVNI and Moonshot both taper to 18mm at the clasp, so a buckle-side 20mm replacement will not match the stock line; the brand's own Moonshot Butterfly Buckle is sold as the 18mm clasp end. Second, base Hydrium stock straps are 22/20, so if you like the factory look, order 22mm tapered, not straight 22mm. Third, Mercury and the bronze Old Radium watches share the 20mm lug width, which is why the brand's suede pages list them together ^[16]; one 20/18 suede serves both. The GMT 0 Cordura and the 24/20 taper is the one place a standard 24mm strap will look wrong at the buckle. Once the width is settled, the watch strap taper chart decodes the second number in listings like 22/20, and the lug width chart by brand places Isotope beside its neighbors.

How this chart was checked

Every quoted line above was re-pulled from the live isotopewatches.com merchant feed at build time (129 products, one page, page two returned empty) and matched verbatim before tabulating ^[23]^[24]. No dealer, retailer or aggregator page contributed a single width. The watchbands.ai brand index was re-checked the same way: its census of 189 brands does not list Isotope ^[25], so no third-party Isotope width chart exists to conflict with this one.