This sensor allows you to choose whether it should function as a cadence meter or speedometer. By changing a small lever, you change what it measures. If you want to measure cadence, you then attach the sensor to the crank arm and if it is speed that is to be measured, it is attached to a wheel. In addition to the sensor, it comes with a rubber cover to put on the back and elastic bands to ensure that the sensor is attached properly. A manual is included that explains the installation. The sensor supports both Bluetooth and ANT+, which means that it can be connected to basically all bike computers and sports watches (for example from compatible with Garmin or Wahoo) or online tools like Zwift. -Color: Black -Size: 29.5mm x 38mm x 9.5mm -Weight: 9.2g -Battery: 220mAh CR2032 -Voltage: 3V -Battery life: 300 h -Standby time: 300 days -Water protection: IP67 -Connection: Bluetooth 4.0 ANT+