Fitment:The windowed 66cc piston kit is only for 80cc/66cc engine kits. Package include: Receive Piston, piston pin, 1 Set of piston rings, 2 piston C Clips， 2*gaskets The windowed 66cc piston kit is only for 80cc/66cc engine kits High Hole Piston; compatible with long connecting rod ONLY; DOSE NOT WORK WITH stocked manifold intake,Buyers must use high performance intake; Work only with better performance manifold intake such as G2 reed,dio reed etc and better performance carburetor such as RT carburetor, CNS carburetor or other ones Work only with better performance manifold intake such as G2 reed,dio reed etc and better performance carburetor such as RT carburetor High Hole Piston; compatible with long connecting rod ONLY;