Before you buy a new band for your watch, make sure you use a band that corresponds to your Apple Watch case size. You can use a band that's designed for Apple Watch (1st generation) and Apple Watch Series 1, 2 and 3 with Apple Watch Series 4 and later and Apple Watch SE as long as the sizes are compatible.

Bands for 38mm, 40mm and 41mm cases are compatible with each other, and bands for 42mm, 44mm and 45mm cases are compatible with each other.

Bands for 49mm cases are compatible with 44mm and 45mm cases. Bands for 44mm or 45mm cases are compatible with 49mm cases.