Comes with two pieces ,the outer diameter is 16mm and inner diameter is 12mm. fit most of brand 110 125 150 250 300 800 1100cc go kart like KANDI,DONGFANG,SUNL, TAOTAO, COOLSTER ,BMS, BMI, NST, DAZON, YONGHE, AMERICAN SPORTWORKS, TRAIL MASTER,CARTER.