Apple Watch
My apple watch 40mm case is aluminum I am looking at it now in new belt sports red color mind its size is 41mm and it is size So will it be suitable for size 40 mm case
Apple Watch Series 6
Question marked as
I assume you meant "band" instead of "mind" in your post.
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, 44mm and 49mm 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 1–12.
For more info, see:
and look at the compatibility Lin k for there band you are interested in.