www.aliexpress.us/item/2251832629610479.html?spm=a2g0o.order_list.order_list_main.45.1b721802bLzW9y&gatewayAdapt=glo2usa i believe it is the 20mm model, but i am not sure. best to spend the couple extra dollars and get the 17mm and 20mm models if you do not know the output shaft size
