Wrist-based heart rate monitor tracks heart rate 24/7. Polar Flow app. Track daily activity. Smart Coaching. Sleep Plus system. Stay connected using the GPS from your smartphone. Receive smart notifications via Bluetooth. Plan workouts and sync to the A370. Provides inactivity alerts. Waterproof to 30 M. Full color TFT display with touch screen. Screen size: 13mm x 27mm. Built-in rechargeable 110mAh battery. Compatible with iOS 7 or later and Android 4.3 or later. Wristband width: 23.5mm. Fits wrists up to 9.5“ circumference.