OEM Replacement Valves are manufactured to OEM specifications from SUH3HT Steel for added corrosion and oxidization resistance.Performance Valves feature a forged one-piece construction, nitride coating, modified radius, swirl polish, chromed stems, and stellite tips. This provides reduced friction for quicker/higher revs and a longer valve life. Heavy Duty Springs RecomendedValve Stainless Psychic Exhaust {Heavy Duty Springs Recomended} RMZ450 05-06