This is a funnel for filling oil/fuel filters the correct way. It filters fluid as you are filling the filter so that the fluid is filtered prior to being pulled through your engine. this also allows for the prefilling of diesel and gasoline canister style filters so you do not have to cycle te key to start the vehicle after a filter change. When prefilling oil filter not only does this filter the oil, but it also make it much easier to prefill your filter. if there if you need an insert for a specific vehicle let me know and ill make an insert with the correct threads. Thank you, let me know what you think.