Features: - Two years warranty - BUILT-IN MEMORY: Heart rate monitor stores 1 heart rate training session. Perfect for sports and activities where a wrist unit would be difficult to use - GoPro COMPATIBLE: Pair your H10 Polar heart rate sensor directly to the GoPro Hero 5 compatibility camera and overlay your heart rate data onto the recorded video. - UPDATEABLE FIRMWARE: Heart rate monitor contains firmware updates that enhance the functionality. - ENHANCED BATTERY LIFE: 400 hours of operation time on a user replaceable battery. Operating temperature - 10 °C to +50 °C / 14 °F to 122 °F - COMFORTABLE FIT: Revised heart rate chest strap design provides the comfort and security needed when exercising. - Compatible with iOS mobile devices iPhone 4s and later and android mobile devices with Bluetooth 4.0 capability and android 4.4 or later.Battery type:CR 2025 - Building upon the legacy of Polar heart rate technology, the H10 is set to be the standard upon which consistent, accurate heart rate recording is based. - Size : One size changeable from 65-93cm - Black -