The 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. Retina display Up to 1000 nits brightness - - High and low heart rate notifications Irregular rhythm notification1 Cardio fitness notifications - Cycle tracking10 Emergency SOS3 International emergency calling2 Fall detection Crash Detection3 High-g accelerometer