Gestures with double tap fingers. Always-On Retina display with 2000 nits. iPhone Precision Finding. WatchOS 10. Electrical heart sensor and ECG app. Sleep app shows time spent in REM Core or Deep sleep. Workout display shows heart rate zones elevation and more. Emergency SOS with fall and crash detection. S9 SIP with 64-bit dual-core processor and 4-Core Apple Neural Engine. Water resistant to 50 M. Midnight aluminum case. Midnight sports band. Case size: 45mm x 38mm x 10.7mm. M/L Band fits wrists 160mm-210 in circumference.