Your controller drives power to your motor and controls its speed, so it&';s important to replace it if yours becomes damaged or broken. We&';ll get the correct replacement to you so that everything will soon be in working order again. Do you know where is the controller in?In the box , which is under the battery. You need to open it by unscrew the nut. NAKTO electric bike controller for classic SKU:D050004S Specification:36V 250W 9pin Model:This NAKTO battery suits for Classic If you still do not know which NAKTO bike controller you need buy,please check with our customer service. Email:[email protected] Shipping:The product usually be dispatched at the same day that orders received, and it usually takes 3-7 days to be delivered. You can get free shipping, and we only ship to the US.