Important note: This piston is for a stock sized bore. Please measure your cylinder to check clearance before ordering. Vertex Four-stroke Pistons: When it comes to power and performance, Vertex four-stroke pistons are hard to beat. Vertex pistons are perfectly suited to handle the rigors and high pressures of today's modern four-stroke engines. Plus, to aid in the break-in process and reduce wear, every Vertex piston utilizes a unique Molybdenum Disulphide (MOS2) coating on the piston skirt. Heat-treated with a T-5 hardening and tempering cycle. Piston skirts are coated with a high-tech Molybdenum Disulphite coating for faster break-in time and increased piston life. Cast piston kits are gravity-cast aluminum alloy (not forged) with 18% silicone content, which produces an extremely light but very strong piston. Forged pistons are forged from 2618 aluminum for superior strength and durability.