These universal oil input adapters have various thread options and a 2-5/8" standard O-Ring. This adapter provides one 1/2" N.P.T. oil input port before filtration. The adapter mounts between the oil filter and block, lowering your filter 1-1/4".This adaptor makes it easy to connect your Accusump to your engine, you will not need to do any drilling or tapping. Remove your old filter, install the adaptor like you would a new filter. Then install a fresh oil filter on the adapter. Then it's time to screw in your feed line from the Accusump, straight into your 1/2 NPT female port on the adaptor. Thread Options are as Follows:3/4" -16 Thread13/16" - 16 Thread18mm -1.5 Thread20mm -1.5 Thread22mm - 1.5 ThreadA range of suitable oil filters can be found HERE.A check valve should not be used with this adaptor.