rear disk brake conversion kit

{"title":"DC 48V Electric Mountain Bike Kit Front \/ Rear Gearless Motor Conversion Kit","imgUrl":"https:\/\/img.silkroadsl.com\/nimg\/9b\/86\/3ea2d4f2e441e8296969cd52e97a-200x200-1.jpg","attrs":{"Price":"$306 PER PIECE","Brand Name":"Suringmax","Model Number":"SR27H-500DF\/DR","Minimum Order Quantity":"1 set","Delivery Time":"20 working days","Certification":"ce","Place of Origin":"Jiangsu, China","Payment Terms":"L\/C, D\/A, D\/P, T\/T, Western Union, MoneyGram","Supply Ability":"10000 sets per month","Packaging Details":"Good quality 5-layer corrugated paper cartons with foam for all the goods","Voltage":"48V","Power":"500w","Color":"Black","Warranty":"3 years","Max speed":"40km\/h","Weight":"6kg","Brake":"V\/Disc Brake","Display":"LCD\/LED","Controller":"48V 22A Controller","Battery":"Optional Lithium Battery","Wheel size":"20-29inch","Dropout":"100mm for front\/135mm for rear","Max torue":"50Nm"}}