Cycling speed sensor for select Garmin wrist-mounted personal trainers and cycling computers Self-calibrating, wireless design measures both cycle speed and cadence in pedaling strokes per minute Provides up-to-the-minute feedback or captures results for later workout analysis Compatible with Garmin Edge 305, Edge 305CAD, and Forerunner 305 Attaches easily to any bicycle; 1-year warranty Compatible with Edge 305/705 and Forerunner 305/405Can also measure rear wheel speed for use on indoor trainer. A good companion for Garmin's Edge series cycle computers and the Garmin Forerunner series, the GSC 10 monitors your cycling rhythm for up-to-the-minute results and later analysis. The self-calibrating, wireless unit measures both speed (in pedaling strokes per minute) and cadence , then provides feedback to the user for optimal performance. You can later feed the results to Garmin's Training Center software, which helps you tailor your workouts to meet specific goals and objectives. The GSC 10 attaches easily to your bike, where its sensors detect signals from your wheels and send the information wirelessly to your personal trainer/cycle computer. It's also backed by a one-year warranty.