Radium Engineering valve for PCV (positive crankcase ventilation) systems. Do not mistake this for a simply one-way check valve. The PCV valve's internal plunger dynamically meters the appropriate amount of crankcase vent airflow based on current engine load. Proper PCV valves prevent the "vacuum leak" that a check valve would create at low loads.
OEM PCV valves rely on two hard surfaces for sealing (some are metal some are plastic). Any because of high volume/low quality manufacturing, many of these PCV valves leak right out of the box. This leak will push positive pressure into the crankcase and create leaking seals and hinder performance. Unlike any other PCV valve (aftermarket or OEM), the Radium Engineering PCV valve features a high temperature silicone seal specifically for managing boost.