The smallest of aFe's Performance Racing Filters are the Crankcase Vent Breathers. These range in size from a .31 inch flange ID to 1.5" ID. Height range from 1.13" to 3". Since these are generally used right up against the crankcase, some of these breathers have a chrome shield to protect the filter from the heat.

To address the need for extra protection from dust and dirt with washable/reusable oil-impregnated cotton gauze filters, aFe developed a new filtration technology so revolutionary that it received a patent. This new filtration technology is aptly called Pro-GUARD 7. Pro-Guard 7 Air Filter has 5 layers of progressively finer mesh medical grade cotton gauze with micro fibers that attract smaller and smaller particles as air passes through is combined with 2 layers of random-porosity non-woven synthetic polyester fabric.

This 7-layer combination of cotton gauze and non-woven polyester is sandwiched between 2 layers of epoxy coated aluminum wire mesh. Because of compression ignition of diesel engines, tolerance are much tighter than in a gasoline spark ignition engine. These tight tolerances require clean air and lots of it. Diesel engine require 7 times more air than a gasoline engine of equivalent size. The patented Pro-GUARD 7 filter media delivers more cool clean air needed for extended engine life, better fuel conomy and additional power.