aFe Magnum FLOW Universal Air Filter w/ Pro Guard 7 Media 4in F x 8-1/2in B x 8-1/2in T x 11in HPro GUARD7 Media: This filter features Pro GUARD7 Media that consists of 5 Layers of progressively finer mesh oiled cotton gauze and 2 layers of finer porosity synthetic non woven media for maximum protection in the most extreme environment. The Pro GUARD7filter media has been tested at 99. 51 percent filtration efficiency. Massive Washable Reusable Filter: With 8 1 2" Base x 8 1 2" Top x 11" Height with a 4" flange, this filter is a flexible flange