Stages magnet-free Speed sensors fit to your hub to provide real-time, accelerometer-based speed data to your cyclometer or phone via ANT+ and Bluetooth Smart. Description -Compatible with most wheels -Installs/removes in seconds -IPX7 Water Resistant -Superlight – just 8 grams -Runtime: 600 hours -Operating range: 2-60 mph -Blue and red LED’s indicate pairing, activation and low battery status