This product has a cylinder inner diameter of 47mm and a piston pin of 10mm.Rapido 50ccTips:1. Please confirm the parts will be fit on your scooter / motorcycle before you place the order.2. If you do not know whether the parts will fit or not, Please send us the photo of your motorcycle or engine by Message.3. This item should be installed by a professional mechanic.4. Some Modified Spare Parts is a small change on your original motorcycle or engine.