Apple Watch cases are sized by your watch case diameter — typically 38mm, 40mm, 41mm, 42mm, 44mm, 45mm, 46mm, or 49mm for Ultra. Check your watch size in Settings > General > About before ordering. Our cases fit Apple Watch Series 1 through 11, SE and Ultra 1 to 3. They don't fit Series 12. Each case lists the exact sizes it fits. Make sure to select the correct size at checkout for a snug, secure fit.