This item is REFURBISHED The largest, most advanced Always-on Retina display yet makes everything you do with your Apple Watch Series 7 bigger and better. Series 7 is the most durable Apple Watch ever built, with an even more crack-resistant front crystal. Advanced features let you measure your blood oxygen level, take an ECG anytime, and access mindfulness and sleep tracking apps. You can also track dozens of workouts, including new tai chi and pilates.