Track your heart rate in real time and view the data on a compatible Velotric display for more informed training and everyday riding. - Optical heart rate monitoring; 40–220 BPM measurement range; - Standard Bluetooth connectivity; automatic reconnection after initial pairing; - Adjustable armband for upper-arm or forearm wear; - Up to 45 hours of battery life; magnetic charging; IP67-rated protection; LED connection and battery indicators. Size 44 × 31.6 × 11.2 mm (~1.73 × 1.24 × 0.44 in) Compatibility Velotric Tempo, Summit 2 (Support heart rate display and Pulse Mode) Discover M, Discover 3, and GoMad (Support heart rate display only)