You can match most bands with any Apple Watch Series 3 or later 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 later. The 40mm and 41mm cases work with band sizes 1–9; the 44mm and 45mm cases works with band sizes 1–12.