All pistons are heat treated with a T-5 hardening and tempering cycle; piston skirts are coated with a hi-tech molybdenum disulphite for faster break-in time and increased piston life Piston kits include piston, rings, wrist pin and circlips Standard pistons and rings are OEM replacements Two-stroke piston kits made from gravity cast aluminum alloy (not forged) with 18% silicone content, which produces an extremely light but very strong piston Four-stroke pistons are forged from 2618 aluminum for superior strength and durability High compression pistons improve power and torque across entire rpm range Big bore pistons increase engine's displacement, torque, and peak horsepower Replacement two-stroke piston rings sold individually; four-stroke piston rings sold as a set