Skunk2 312-05-0010 Valve Spring Base/ Locators K20A - K20A2 - K20Z1 - K20Z3 - K24A2 - F20C - F22C Chromoly Spring Base w/ .440" ID Spring Step - Use on K Series Engines Originally Equipped w/ Single Valve Springs - MUST BE USED TO INSTALL DUAL VALVE SPRINGS IN SINGLE SPRING K SERIES HEADS OR K SERIES SPRINGS IN F20C/ F22C HEADS.