Breather boxes have long been used to improve crankcase ventilation.  If installed properly, it can help remove the oil mist from the crankcase fumes that are expelled while the engine is running, especially under load. The oil is accumulated and returned to the crankcase via the hoses.  Less crankcase pressure can help prevent and resolve oil leaks.  This kit comes with the necessary hoses, fittings, and box to ventilate the crankcase from your oil filler at the alternator/generator stand, and both valve covers.  Generally, this box is installed on the firewall, but it's also been installed on the front or back of the fan shroud, or on a roll cage in an off road car.  Make sure when you install it, you route the hoses so they always have a downward slope to where they return the oil back into the crankcase.  We've found it's also much better to remove the foam insert that comes with these and replace it with Scotchbrite™ or a similar product that will allow it to pass more air through, and not get gunked up.