This controller is only compatible with Wildeway FW11 3.0 and FW11S 3.0 e-bike, not compatible with Wildeway FW11/FW11S 4.0 e-bike, X7 e-bike and KW26 e-bike. Please check your model before buy it. If you place a wrong order, we are not responsible for it. If you are unsure about the model of your bike, you can contact us through our official email before placing an order(wildewayebike@outlook.com).