Features:This sensor collector can collect the cycling speed to help you ride in safe speed and protect your body.Sensitive chip supports bluetooth, suitable for working with bike computer, smartphone, etc.Ultra light and mini size, with strong sticker on the back, comes with a strap for firmer installation on bike hub.Waterproof grade is up to IP7, shows no fear to harsh weathers.With built-in battery, standby and working endurance are up to 300 days.Specification:Material: ABSColor: BlackWaterproof: IP7Battery: 1 x CR2032 battery (included)Endurance: Approx. Standby-450 days; Working-300 hoursConnection: Bluetooth 4.0, ANT+Detection Range: 0-70 km/hSize: Approx. 15 x 28 x 38mm / 0.59 x 1.1 x 1.5inWeight: Approx. 24gPackage List:1 x Wireless Bike Speed Sensor1 x Battery2 x Rubber Bands