if you like me I keep losing mine so easier to have one on each bike, these handy sensor you don't need to take the battery out drop it fumble around reinstall the battery put the cover back on blah blah, just turn the cover plate to what you want it to do.
C3 Bike Cadence
Speed Sensor -
Color: Black -
Size: 29.5mm38mm9.5mm -
Weight: 9.2g -
Battery: 220mAh CR2032 -
Voltage: 3V -Function: Track cycling speed or cadence
-Using time: 300 hours -
Standby time: 300 days -
Waterproof: IP67 -
Link method:Bluetooth 4.0 ANT+ -
Compatible: ANT+ sports watch like Garmin, TomTom.. ANT+ bike computer like Garmin WahooBryton Online game Zwift, Tacx, BKOOL -
Supported devices: Bicycle riding APP, Bicycle trainer software, Bicycle stopwatch etc.