Key Features LTPO OLED Always-On Retina display Wide-angle OLED Up to 40% brighter when viewed at an angle High and low heart rate notifications Irregular rhythm notifications Low cardio fitness notifications Sleep Tracking Sleep apnea notifications Water resistance 50m (swimproof) Bluetooth, GPS, Wi-Fi Up to 36 hours in Low Power Mode Built-in rechargeable lithium-ion battery ECG app S10 SiP with 64-bit dual-core processor iPhone Xs or later, including iPhone SE (2nd generation or later), with iOS 18 or later