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