This is a keyed damper to fit the Massive Speed keyed crankshafts. Some say this is unnecessary, but far too many people fall victim to slipped timing because the damper is overlooked during the keying process. The damper will include a 3 mm key with a specific length such that you will simply add the key to the existing keyway in your crank and slide on the damper! No need to disassemble the front of the engine! And will also come reinforced so the trigger wheel won’t fly off!