Will it fit

I’m looking into buying a bumper case with built in straps for my Apple Watch. It says it’s compatible with all series Apple Watches and 42/44/45/49 mm and 41/40/38 mm! I have the 42 mm series 3 I’m wondering if it actually will be compatible with mine because the series 8 isn’t the same size as the 3 and cases aren’t compatible with it.