Top End Piston Kit - 101.95 mm - Yamaha The piston is heat-treated with a T-5 hardening and tempering cycle, The piston skirt is coated with high-tech Molybdenum Disulphite to allow faster break in time and increased piston life, Cast piston kit is gravity-cast aluminum alloy (not forged) with 18% silicone content, Replica piston and all rings are OEM s, Top end kit includes piston, rings, pins, circlips, top end gaskets and cam chain