Pistons are pre fitted to cylinders with head gaskets and can be used with stock heads. No crankcase machining required for installation. Great customer service is very important to us here at J&B Cycles. We are dedicated to our customers and will go the extra mile to make your experience nothing less of perfect.You may return any part within 14 days from the original invoice date. COD packages will not be accepted. Origin written on parcel label.