Supertech Black Nitrated Intake Valve STD Size Set of 8Note: Must use single groove keeper part# KPR 6S 7 (two per valve) We apply more than 30 years of experience in the development of each and every Supertech racing valve we sell. Combine this experience with state of the art equipment such as ultrasonic tests, x rays, laser measurement equipment, and applications like computerized Finite Element Analysis (FEA) and it is no wonder why supertech has some of the best performance products on the market.