This steel oil pump gear is by far the best upgrade to the FD501D and FD620D series of engines. The original plastic gear is made of a similar plastic grade as the plastic cam gears were made of and so they will fail just like the camshaft gears did. On most applications that had the FD620D engines and its similar models when the gear goes usually the engine goes as well because there was no oil shutoff on the engine when oil pressure was lost. We recomend changing this gear whenever the engine is appart for any reason to be sure you wont ever loose oil pressure if proper oil levels are maintained. The cost is much higher than the original gear but this gear will outlast the life of the engine unlike the plastic one. If you have any questions feel free to give us a call.