*This item is USED. Always-on Retina display has nearly 20% more screen area than Series 6, making everything easier to see and use The most crack-resistant front crystal yet on an Apple Watch, IP6X dust resistance, and swimproof design Measure your blood oxygen with a powerful sensor and app Take an ECG anytime, anywhere Get high and low heart rate, and irregular heart rhythm notifications Stay in the moment with the new Mindfulness app, and reach your sleep goals with the Sleep app Track new tai chi and pilates workouts, in addition to favorites like running, yoga, swimming, and dance Track your daily activity on Apple Watch, and see your trends in the Fitness app on iPhone Sync your favorite music, podcasts, and audiobooks Pay instantly and securely from your wrist with Apple Pay All-day battery life and faster charging⁵ watchOS 8 introduces new workout types, the Mindfulness app, the new Portraits watch face, and enhancements to Messages Apple Watch Series 7 requires an iPhone 6s or later with iOS 15 or later.