If you are running an On 3 Performance Ceramic Ball Bearing turbocharger with a 65mm exhaust wheel, you will absolutely need this. If you run a standard -3 or -4 feed up to the turbo, you will most likely start seeing oil in the compressor or smoke under boost coming out of the tail pipes. This is our restrictor fitting which cuts the oil volume down to what the turbo requires to operate. Again, this is for our 60, 67 and 76/65 cBB turbos only! Do not use this with a 75mm exhaust wheel or larger cBB turbo! If you do, there is a very good chance you will starve the shaft of oil and the turbocharger will fail. Some customers running the On 3 Performance Journal turbochargers also may possibly require this with high volume oil pumps. In most cases where you are seeing around 60psi or more under load, you might consider running this if you are getting any oil passing through the seal. Sometimes (in very rare cases,) on the GM LSX based platforms, we run these even on the journal bearing turbochargers due to the engine oil pressure this is the last thing you want to try. Make sure your drain is set up 100% properly and that both of your PCVs are vented to atmosphere, or if you are using a catch can, that it has a larger breather on it. Again, be very cautious with this because you can starve the turbo of oil. Please call us directly with any questions, or concerns!!