Top End Kit - Standard Bore 94.95mm, 13:1 High Compression For 2009 Yamaha YFZ450R ATV All pistons are heat treated with a T-5 hardening and tempering cycleAll piston skirts are coated with a high-tech Molybdenum Disulphite coating for faster break-in time and increased piston lifeCast piston kits are gravity cast aluminum alloy (not forged) with 18% silicone content, which produces an extremely light but very strong pistonForged pistons are forged from 2618 aluminum for superior strength and durabilityForged High Compression pistons improve power and torque across entire rpm rangeBig Bore pistons increase engines displacement, torque, and peak horsepowerForged Replica pistons are forged OE replacementsReplica pistons and all rings are OEM replacementsTop end piston kit includes piston, rings, pins, circlips, top end gaskets, and wrist pin bearing when applicableReplacement two-stroke piston rings sold individually; four-stroke piston rings sold as a set *Bore Diameter: 94.95mm ^ Compression: 13:1 High Compression ^ Sizing: Standard Bore