Used for <2 years, works great but just got a new watch! Built-in rechargeable lithium-ion battery, Up to 18 hours Sleep tracking Cycle Tracking with retrospective ovulation estimates Compass Always-on altimeter Water resistant up to 50 meters Certified IP6X dust resistant Blood oxygen sensor (Blood Oxygen app) Electrical heart sensor (ECG app) Third-generation optical heart sensor International emergency calling, Emergency SOS, International roaming High-g accelerometer Up to 256 g-forces with Fall Detection and Crash Detection High dynamic range gyroscope Ambient light sensor Speaker Microphone Apple Pay GymKit Capacity 32GB Ceramic and sapphire crystal back