The PERMIT" Filter: filter/muffler design, with bolt flanges and standard design with end cones. PERMIT" Filters from CleanAIR Systems are designed to control particulate matter (PM), carbon monoxide (CO) and hydrocarbons (HC) from any size diesel engine. Utilizing a wall-flow ceramic filter coated with CleanAIRs unique catalyst, the catalyzed particulate filter dramatically reduces black smoke and odor associated with diesel exhaust. The PERMIT" Filter is packaged in a 304L stainless steel shell, finished by bead blasting, offering a highly corrosion-resistant product that will last for years. All PERMIT" Filters are available as standard filter design, filter/muffler design or filter/silencer design