The new bracelet sizes are also compatible with older watch models. There are no restrictions on the Watch series or editions that can be used with each watch band. All Apple watches have the same connector size and shape. It's possible with Apple leather straps, but all the others that have the adapters built in won't work.
However, just like all previous bands fit the Apple Watch Series 7, these 41mm and 45mm straps are compatible with previous watches. Leaks and conflicting rumors prior to the presentation suggested that the new 41mm and 45mm Apple Watches would therefore require new straps. Remember that since all bands will be compatible with the new Apple Watch, there's no reason to wait for the launch of Apple Watch Series 7 to buy new bands if you're looking for a new look. Weinbach's information that the new Apple Watch “will use different straps that won't be compatible with old watches is open to interpretation, at best.
While it may seem at first that Apple has unceremoniously eradicated support for all previous models, don't worry, it didn't. While I think the new straps will be labeled 41mm and 45mm, that doesn't mean they won't work with older watches. Contrary to some rumors prior to the event, the redesigned Apple Watch Series 7 will not require new watch bands and will continue to be compatible with all previous ones. To reiterate, bands made for the smaller of the two new sizes work with previous smaller Apple Watch models, and vice versa.
Apple Watch models with 40mm and 41mm diameter straps can be equipped with individual loop straps in sizes one to nine, while models with 44mm and 45mm diameter straps can be equipped with straps from four to twelve. Luckily, Apple has stated that all of the above bands will work with the Apple Watch Series 7, so you don't need to replace all of your best Apple Watch bands if you plan to buy the newest Apple Watch. Apple didn't create a Magic Keyboard for iPad mini 6, and Lululook's magnetic keyboard may be a testament to why. For the 40mm and 41mm Apple Watch models, you can get individual loop bands in the size range of one to nine, while the 44mm and 45mm models work with band sizes four through 12.So, that means Apple has to make new straps that are compatible with at least the SE or make straps that are only going to work for this year's models, again unlikely to the point of being unthinkable.
I think Apple may be exercising great perfectionism here, and for most people the difference is too small to worry about. In case you didn't know, they're only compatible with Apple Watch SE, Series 4, and newer models.