FMF Racing Powercore 4 Hex Aluminum Slip-On Muffler w/Stainless End Cap for Yamaha WR450F 12-15FMF PowerCore 4 HEX Slip On Exhaust Yamaha WR450F When designing the PowerCore 4 HEX Exhaust, FMF took a hard look at their top of the line mufflers to produce race inspired performance at a more economical price. The end result is a quality muffler that delivers improved torque, increased horsepower and rugged durability all at a price that won't break the bank. Features: Increase in power and torque through entire RPM range Durable stainless steel