Redesigned and re-engineered with built-in electrical and optical heart sensor, a new Digital Crown with haptic feedback and varying heart rate notifications. For fitness fans, it has New Breathe watch faces, auto workout detection, new yoga and hiking workouts and advanced running features. Plus, new head-to-head competitions, activity sharing with friends, personalised coaching, monthly challenges and achievement awards. On top of all these amazing features, it's also swim-proof, has a 30% larger display and 50% louder speaker than the S3. For those always on the go, Cellular watches can connect to mobile data networks as well as WiFi. Where WiFi is unavailable, you can insert a Nano-SIM from major network providers to keep connected whilst out and about (check participating networks for available data plans). So, you can send, receive and make calls right from your wrist. Connectivity16GB memory. iOS operating system. Bluetooth 5 connection. Wi-Fi. Display information40mm AMOLED screen. Touchscreen. BatteryTypical usage time of up to 1 day. Low usage time of up to 0.75 day. Physical specificationSize: large. T10.7mm. Weight 36.7g. FeaturesWater resistant. Dust resistant. Make calls. Answer calls. Read texts and reply to texts. Read emails and reply to emails. Receive social network notifications. View calendar. Displays weather. Music player. Heart rate monitor. Pedometer. Accelerometer. GPS. Accessories included: Case, Band, 1m Magnetic Charging Cable and 5W USB Power adapter.