Monitor your pedalling cadence and/or speed as you ride with these easy-to-install wireless sensors. Simply attach the sensors & ride. With no magnets or other exposed parts to line up, these sensors are easy to install, maintain & move between bikes. The cadence sensor fastens to any crank arm size & measures pedal strokes per minute so you can get the most out of your training. The speed sensor attaches to the hub of either wheel & self-calibrates with your Edge® to give you accurate speed & distance at all times, including indoors on the turbo trainer. Combine them both & improve your personal best or see where your stand against the pros. In the Box: Speed sensor Speed sensor sleeve Manual Please note: The speed sensor is water-rated to 1 ATM; ANT+ wireless connectivity does not work underwater.