Vertex Top End Kit 4T YZ250F Compr. 13.5:1 2016-18 (76.96) Forged pistons are forged from 2618 aluminum for superior strength and durability Forged high compression pistons improve power and torque across entire RPM range Pistons are heat treated with a T-5 hardening and tempering cycle T-box forgings and DLC-coated wrist pins on forged pistons with highest compression ratios for increased strength and performance All piston skirts are coated with a high-tech molybdenum disulphide coating for faster break-in time and increased piston life Forged replica pistons are forged O.E.M replacements All rings are O.E.M replacements Top end piston kits include piston, rings, pins, circlips, top end gaskets and wrist pin bearing when applicable