Valve clearance is easy to adjust on all push rod engines or OHC engines with top adjustment. Clik-adjust makes the job easier & absolutely precise. This essential clearance adjustment ensures the valves (inlet & outlet) open & close correctly resulting in better engine performance. Adjusts tappets precisely Micro adjustment No need to use feeler gauge after its set up. Suits all push rod valve engines & OHC engines with Flat head top adjustments screws. 1/2D for any size lock nut. Essential for worn tappets