FITMENT: The Valve Spring Compressor and a Rocker Arm Tool fit for 1999~2013 Jeep, Dodge, Chrysler 3.7 and 4.7 engines. Alternative to Mopar Miller 10102-8426, 8387 and 8516A. FUNCTION: This special rocker arm remover used to allow removal of the camshaft, rocker arms and hydraulic lash adjusters in 3.7 and 4.7 Liter Engines. Also can be used to change broken valve springs or just to install replacement rockers or lifters. ADVANTAGE: .