Air Oil Separator - Return ( AOS-R ) Kit For FR-S / BRZ / GT86 / GR86 Radium Engineering - USA_RAD-20-0351 - COMPATIBILITY12-16 Scion FR-S (LHD)12-21 Toyota GT86 (LHD)12-20 Subaru BRZ (LHD) High-powered modified Toyota 4U-GSE and Subaru FA engines tend to generate excessive blow-by oil and gasses. In these cases, an ordinary small catch can may quickly fill with oil and not be adequate. Like the Radium Engineering Dual Catch Can Kit, the AOS-R (Air Oil Separator-Return) kit is responsible for keeping blow-by oil and other pollutants out of the intake pipe, manifold, turbocharger, and intercooler during all engine loads. The main difference is that an AOS-R system returns what is collected back into the oil pan (as shown below) so there is no servicing required. The built-in heater keeps water from condensing in the AOS-R. And because water is more dense than oil, there is an integrated water trap found around the bottom perimeter of the can. DIMENSIONSAOS-R Height: 6.3" (without fittings)AOS-R Diameter: 3.45" Round AOS-R Capacity: 20.3 oz (600m L) PORTS Inlet: 7/8"-14 threaded for 10AN ORB fittings Outlet: 7/8"-14 threaded for 10AN ORB fittings Return: 7/8"-14 threaded for 10AN ORB fittings Coolant: 7/16"-20 threaded for 4AN ORB fittings (x 2) BENEFITS-Effectively raises the octane and increases engine performance with cleaner inlet air -Prevents oil buildup in the intake or intercooler system walls, throttle body, intake manifold, etc.-Lowers hydrocarbon emissions NCLUDED-Machined alumium Radium Air Oil Separator-Specially designed mounting bracket-SAE J30R7 rated PCV/Emissions hose-Coolant heater hoses and fittings-All necessary aluminum fittings and hose-ends-Stainless steel mounting hardware  Instruction PDF