If you have the Panasonic electric bike motor in either 26 volt or 36 volt then this is the motor drive sprocket you need when the one you have is worn out. This 11 tooth motor drive sprocket is used on bikes that want more speed and are pedaled at a higher cadence. If your bike has a 9 tooth sprocket then this gear will give you more speed and allow you to pedal at a higher cadence. It is a direct replacement part. It is important to replace this sprocket when you replace the chain otherwise you will experience chain skipping.  This is the stock drive sprocket that came on the Kalkhoff Pro Connect Sport ebikes with 26v Panasonic motor systems