Monitor your performance as you ride with this easy to install wireless speed and cadence sensor bundle the cadence sensor fastens to any size crank arm and tracks pedaling strokes per minute so you can train for your optimal performanced the speed sensor attaches to the hub of either wheel and self calibrates with your garmin edge to give you accurate speed and distance at all times even when indoors on the turbo trainer or in areas where gps signal is interupted compatible with the ed