The Apple Watch SE (2nd generation) aluminum case is lightweight and made from 100 percent recycled aerospace-grade alloy. The Sport Band is made from a durable yet surprisingly soft high-performance fluoroelastomer with an innovative pin-and-tuck closure. 1.57″ Retina LTPO OLED 40mm WatchOS 9.0, upgradable to 9.2 Bluetooth v5.3 50m water resistant High and low heart rate notifications Irregular rhythm notification Cycle Tracking Fall Detection, Crash Detection