These Super 40 Flowmaster mufflers significantly outflow the older two-chamber mufflers. They help create even more horsepower with less interior noise and a deeper exterior sound. These mufflers feature a design patterned after Flowmaster's race mufflers. These Flowmaster mufflers far exceed older models on Dyno tests. They create a beautiful hot rod sound, along with increased horsepower and gas mileage. So, if you want to get that hot rod sound and add some horsepower, then these Flowmaster mufflers have you covered.