Over 65psi of retarding back pressure; BD's exclusive Variable Orifice Technology; Adjustable pressure regulation; Pneumatic spring loaded cylinder; BD's solid, offset butterfly; Rugged, cast-iron housings; BD's exclusive alumibronze bushing; Piston ring-seals; Stainless steel butterfly shaft; Proven to stand-up under the harsh, high heat conditions of the exhaust environment; IP67 sealed air compressor included; Warm Up mode available to help bring engine up to normal operating temperature quicker when at idle; Kit fits 4in and 5in exhaust; All mounting hardware provided; There's a reason why the BD Brake is the most widely-recognized diesel exhaust brake in the industry: It's the best! Compare it to the competition, and you'll see why.