This is focused around preventing oil puking out of valve covers on boosted applications.
These are designed to fit 1980-1988 Buick Regal, Pontiac Grand Prix, Olds Cutlass, Chevy Monte Carlo, and Malibu.
How this works. Pressurized air out of the valve covers which is also carrying oil enters the side of the box. This oil and air mixture has to pass through the aluminum vent holes in the internal breather plate, then through packed steel wool, then out the breathers on top the box. The steel wool will absorb the oil that makes it up through the vented holes in the internal plate. This will prevent the oil from puking and spraying all over the engine bay. A very common problem for boosted applications. These will come -8 drain cap that can be opened to release the excess oil the box traps. On the side it will come with an 1/8 NPT plug which can be removed and used for transmission vent control. You have the option to choose dual -12AN inlets or 3/4 NPT inlets.