Piston Kit - 83.94 mm - Yamaha YFM350 Raptor / YFM350X Warrior The piston is heat-treated with a T-5 hardening and tempering cycle, The piston skirt is coated with a high-tech Molybdenum Disulphite coating for faster break in time and increased piston life, Cast piston kit is gravity-cast aluminum alloy (not forged) with 18% silicone content, Piston kit includes piston, rings, wrist pin and circlips