The Hooker Maximum Flow muffler actually flows 99% and produces more horsepower and torque than a 2-1/2" open pipe. The Maximum Flow is constructed of an aluminized steel case with stainless steel internal core and uses a high temperature packing material to absorb excessive noise while allowing a mellow powerful sound. As with all absorption type silencers, the Maximum Flow will be most effective for sound control with lower compression (8.5 to 1 and lower) motors with conservative Camshafts and with applications using catalytic converter(s). The Maximum Flow flows either direction, allowing for easy installation.