This tool makes it easy to upgrade your soft stock valve springs on your mercedes diesel engine. Save the time and money pulling the cylinder head, rotate the engine 120 degrees at a time to change (1,6),(2,5)(3,4) the piston will keep your valves from falling out. It simpliy threads into the valve cover bolt holes, you can change several valves at a time before moving the jig. The fully adjustable compression tool allows for full travel to issure space between the keepers.