Stages magnet-free Cadence sensors fit to your crank arm and rear hub to provide real-time, accelerometer-based cadence data to your cyclometer or phone via ANT+ and Bluetooth Smart. Description -Compatible with most crank arms -Installs/removes in seconds -IPX7 Water Resistant -Superlight – just 8 grams -Runtime: 600 hours -Operating range: 18-200 rpm -Blue and red LED’s indicate pairing, activation and low battery status