When designing the PowerCore 4 HEX, we looked at our top of the line products to deliver race-inspired performance at an economical price. The end result is a quality muffler with improved torque, increased horsepower and rugged durability all at a price that won't break the bank. -Overall increase in power and torque. -Durable stainless steel and aluminum construction. -Space Age internal packing material for maximum longevity. -Internal shape of core uses Hi-Flo technology. -Enhanced sonic evacuation provides for higher flow and increased power. -Includes removable spark arrestor. Make Model Year YAMAHA WR450F 16-18 YAMAHA YZ450F 14-17 YAMAHA YZ450FX 16-18 Fits: Yamaha WR450F 2016-2018 YZ450F 2014-2017 YZ450FX 2016-2018