Dinan D660-0077-BLK is a free-flow axle-back exhaust for 2017-2020 BMW 440i models using the F33/F36 chassis. The system uses T304 stainless steel construction with black ceramic-coated tips and is designed to reduce back pressure for improved exhaust flow, power, and sound. Dinan lists maximum gains of 6 HP at 6600 RPM and 5 lb-ft at 6600 RPM, with a 1.2-hour installation time. The system is engineered to retain a civilized tone during normal driving while becoming more aggressive under hard acceleration. Dinan lists this component as emissions-neutral.