49mm

Swimproof: IP6X dust resistant, MIL-STD 810H certification, Action button

Always-On Retina display: Upto 2000 nits

Blood Oxygen app

ECG app

High and low heart rate notifications

Irregular rhythm notification

Temperature sensing

Cycle tracking with retrospective ovulation estimates

Emergency SOS , International emergency calling, Fall Detection, Crash Detection, 86-decibel Siren to attract attention

Cellular available, Family Setup — pair multiple, watches with one iPhone