Premium Stainless Steel: The Performance Series valves are available as XH-422 for exhaust and NK-840 for intake, constructed from high-quality stainless steel for optimal performance.Chrome Stems and Hard Tips: These valves boast chrome stems and hard tips, ensuring exceptional durability, even under extreme conditions.Swirl Polished and Fully Machined: The under head areas are expertly swirl polished, and the combustion faces are fully machined, optimizing airflow and combustion efficiency for maximum power.Variety of Lengths: Tailor your valve selection to your engine's needs with options for stock length or .100? longer lengths.