Features an oil metering design that provides uniform metering throughout the entire rpm range Rollers and axles are manufactured from high-carbon/chromium bearing-quality steel, which is through-hardened for improved wear and load-carrying capability, and the pushrod seat is carbo-nitrided Each unit is 100% tested for proper function HY-REVĂ– hydraulic roller lifter features internal hydraulic check valve, which allows for higher rpm Made in the U.S.A. PRO-MAGNUMĂ– hydraulic roller lifter requires adjustable pushrods.. HY-REV LIFTER 91-99 XL