Apples series 6 watch case
Will a 42mm case fit my 40mm watch or would a 38mm fit it better?
Apple Watch Series 6, watchOS 7
You can match most bands with any Apple Watch Series 3 or newer case of the same size. The 41mm bands work with 38mm and 40mm cases; the 45mm bands work with 42mm and 44mm cases.
The Solo Loop and Braided Solo Loop bands are only compatible with Apple Watch SE and Apple Watch Series 4 or newer. The 40mm and 41mm cases work with band sizes 1–9; the 44mm and 45mm cases works with band sizes 4–12.
For more info, see: