This pulley is a big help if you have wobble problems with your original pulley. Sometimes the end of the crankshaft where the pulley rides gets worn and the original style pulleys just don't run true. This pulley is slit so once it is slid into position and the ratchet pin is in place, there is an allen headed set screw that will lock the pulley tightly on the crankshaft. The absence of ribs on this aluminum pulley gives the pulley enough clearance to slide over the crankshaft with the oil pan in place. U.S.A.