UPR's Catch Can Diffuser eliminates oil contamination. UPR's Catch Can Diffuser was designed by analyzing the fluid, vapor and airflow characteristics unique to the internal combustion engine. Resulting in a multi-level design to maximizes the control of oil solids and vapors. UPR's Catch Can Diffuser offers multiple benefits: First, by vertically spacing the inlet screen to a position lower than outlet screen, oil which collects on the inlet screen is inhibited from migration to outlet screen. Thus, the amount of oil entering the exhaust side or outlet is substantially reduced or eliminated. Secondly, it makes it possible to adjust which side of the catch can is the inlet or outlet by simply installing the UPR diffuser in either chamber of your catch can. This eliminates oil pulling through the air with the single level chambers. Most importantly, the UPR Catch Can Diffuser allows the oil and condensation to properly cool and disperse from vapor back to liquid. The extended multi-level design is the key to proper Coalescence within the UPR diffuser and its baffling media. Coalescence is a process that allows droplets, vapor and particles to merge and form into a larger liquid state and collect into a more controllable form. This Exclusive design maximizes Coalescence, increasing the catch cans efficiency and it's ability to collect oil vapor. The UPR Catch Can Diffuser virtually eliminates you from getting any contamination into your intake tract or combustion chamber. Fits all UPR Catch Cans made before June 2013.