Apple introduced a "new" 42mm smaller size, and with that, added a whole lot of confusion to band compatibility. The Sport Loop and Milanese Loop now come in 40mm, 42mm, and 46mm variants.
From one of their updated watch strap pages:
> Strap Compatibility
> You can match most straps with any Apple Watch Series 3 or later case of the same size.
> 40mm, 41mm and 42mm straps are all compatible with 40mm, 41mm and 42mm case sizes. 44mm, 45mm, 46mm and 49mm straps are all compatible with 44mm, 45mm, 46mm and 49mm case sizes.
> The Solo Loop and Braided Solo Loop straps are only compatible with Apple Watch SE, Apple Watch Series 4 or later and Apple Watch Ultra or later.
> For Solo Loop and Braided Solo Loop, the 40mm, 41mm and 42mm cases are compatible with strap sizes 0–9; the 44mm, 45mm, 46mm and 49mm cases are compatible with strap sizes 0–12.
I'm having such a hard time trying to parse this, especially since Series 3 was available in 38mm and 42mm variants, and it was Series 4 that upped the numbers to 40mm and 44mm.
I use the original band from my 38mm S3 on a 40mm S6, it definitely fits perfectly between them
But I bet they omitted the original 38/42 sizes from that list because now it overlaps with 42mm being the small size of S10
Sizing the watches by mm instead of naming them small/large feels like a weird relic from the original apple watch launch when it came in a $10,000 gold version and Ive was positioning it as a fashion item
I think the most plausible reason to do this would be to avoid future confusion if they decide to introduce new band sizes.
Also, the current differences in case sizes mean that band sizes are slightly different when used with different watch models, even if the band width is the same. The same solo loop on a 38mm watch fits slightly smaller than the same exact band on a 40mm watch, even if they're the same mounting mechanism. So, to be precise about fit, you already need to specify the watch size specifically, even if the band width is the same.
Captain Axually checking in to say that there three widths. The Ultra is wider enough that the “large” bands, though they fit the Ultra, leave a bit of a noticeable gap where the band hardware slides in.
From one of their updated watch strap pages:
> Strap Compatibility
> You can match most straps with any Apple Watch Series 3 or later case of the same size.
> 40mm, 41mm and 42mm straps are all compatible with 40mm, 41mm and 42mm case sizes. 44mm, 45mm, 46mm and 49mm straps are all compatible with 44mm, 45mm, 46mm and 49mm case sizes.
> The Solo Loop and Braided Solo Loop straps are only compatible with Apple Watch SE, Apple Watch Series 4 or later and Apple Watch Ultra or later.
> For Solo Loop and Braided Solo Loop, the 40mm, 41mm and 42mm cases are compatible with strap sizes 0–9; the 44mm, 45mm, 46mm and 49mm cases are compatible with strap sizes 0–12.
I'm having such a hard time trying to parse this, especially since Series 3 was available in 38mm and 42mm variants, and it was Series 4 that upped the numbers to 40mm and 44mm.