Retro-Fit Street Chevrolet Mark IV, Gen 5/6 Hydraulic Roller Lifters Designed for street performance enthusiast who want to upgrade to a hydraulic roller camshaft. Manufactured to fit early or late model blocks, including blocks with tall lifter bosses. Cold form technology shapes the body for durability. Carbonitride and tempered for hardness. The roller wheel is hardened and tempered steel alloy. Heat treated stainless steel cross bars. High alloy steel tie bar buttons. Note: Specifically designed for street applications to 6500 rpm. Made in the USA!