Measures your speed & distance Comes with a CS series bike mount Wireless connection with cycling computer Easy to attach to your bike Comes with all necessary attachments The CS series speed sensor is attached to the wheel of your bike & measures your speed & distance throughout your ride. It will send the data to your bike computer that will show you the data during your exercise. The CS series speed sensor is compatible with; Polar CS100b Polar CS100 Polar CS200 Polar CS200CAD Polar CS300 Polar CS400