We guarantee it will out-perform any cast aluminum exhaust system!That is a promise no one else dares to make!The innovative Thunder & Lightning bolt-on cast aluminum exhaust header boosts your engine's performance 35-100HP! This unique foundry-tough cast tube style header incorporates four individual water jacketed 32" long runners and easily bolts on to most big block Chevy marine engines, including Mercury Bravo, Speedmaster, and Volvo installations.