Reverses the rear cam's direction of rotation, providing additional operating clearance between cam lobes; as a result, higher cam lifts are possible. High lift camshaft for modified engines with 106" or greater displacement and compression ratios between 10.0:1 to 11.0:1. Increases valve and timing accuracy by eliminating timing chain lash and loosely-fit stock chain drive. Works with stock, unported heads, but S&S CNC ported heads are recommended. Material must be removed from inner surface of the stock gear cover to install. A hydraulic press and other professional level tools are required to install. S&S requires that adjustable pushrod/cover kit be used. Cam bearings and gaskets must be replaced when installing new cams. Best power from 3000-6000 rpm. This is not a bolt in camshaft kit. Kit includes camshafts, inner gear, out gear drives, inner bearings, outer bearings, gaskets and instructions. Made in the USA. Installer must check coil bind, valve to valve clearance and valve to piston clearance.. Due to the inherent characteristics of gear drives, you may experience more valve train noise..