Two Brothers Racing 005-4070106-S1B S1-R Full System - Aluminum Muffler The S1R exhaust is a state-of-the-art product from Two Brothers Racing. The system features carbon fiber highlighted by a natural finished Aluminum outlet and stamped spring-mounted inlet for ultimate durability. The S1R exhaust from Two Brothers Racing showcases a race design while increasing all-around performance. All carbon parts are made with a high temp aerospace grade epoxy resin. The carbon fabric is made with a 33 million modulus carbon tow then impregnated with the high temperature resin under very tight tolerances. Aerospace high-temp carbon fiber