16-18 KAWASAKI ZX10R: Two Brothers S1R Slip-On Exhaust (Carbon Fiber) The S1R exhaust is a state-of-the-art product from Two Brothers Racing. The system features carbon fiber, aluminum or stainless steel highlighted by a natural finished aluminum or stainless steel 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. S1R Slip-On Exhaust. Aerospace high-temp carbon fiber, high-temp stainless steel or natural-finished aluminum canister.