Turbochargers need oil running through them constantly to run effectively, but in ball bearing turbos they need a lower flow of oil than journal bearing due to cartridge design. this is where oil restrictors come in. if you aren't using a restrictor and having oil leak through the seals, you need to install one before the seals leak more oil over time. The other benefit is improved boost response due to less windage of oil in the bearing. Oil pressure entering a ball bearing turbocharger needs to be between 40psi and 45psi at the maximum engine operating system. many engines are higher than this, so need to utilise one of our 0.035" restrictors. As most oil lines are AN3 or AN4 we have a fitting for each type with a standard turbo thread on the other end (7/16").