This sensor is 2 parts. The wheel needs to attach to the exposed part of the bottom bracket, where the crank arm attaches. The sensor attaches to the seat tube of the bike frame. The wheel with magnets close passes the sensor which tells the controller to give power to the motor. This magnet wheel has 12 magnets which ensures that the turning of the pedals gives a more natural feel to the motors assist. The magnet wheel splits in 2 to enable it to be easily fitted without having to remove the crank arm. Cable Length = 225mm to the end of the connector Weight = 58g Magnet disc dimensions = 86mm diameter, 5.5mm thick Connector Type = 3 Pin Higo Waterproof NOTE A – If running a front derailleur (front gears) then sometimes the mech can snag with the sensor that attaches to the seat tube. Most of the time you can slightly move the position of either the mech or the sensor and all is OK. However, we would always recommend running a single sprocket at the front once you have converted to E-Bike, as the assist will largely erradicate the need for all those gears and unneccessary maintenance!  NOTE B – Make sure your sensor is aligned correctly with the magnets. The distance between the magnet on the disc and the sensor should be no more than 3mm. This PAS sensor is to be mounted on the right hand drive side of the cranks. NOTE C – These are compatible with all the Bafang controllers we sell. If you plan to use it with a different controller, ensure the pinout is the same by comparing the pinout in the product photo to the specification you require