HMF Exhaust Performance Series: The Performance Series from HMF has been the staple of the brand since it’s origin. Whether on dirt or pavement, this exhaust system has the capability of generating an even increase in horse power and torque while distributing an aggressive deep sound. The Performance Series is assembled on an durable 6063-T6 aluminum alloy shell, with magnesium and silicon as the alloying elements. A high-temp powder coat can be applied for a completely custom look. Featuring a 2 1/8″ unrestricted core, the Performance Series core has a special hole pattern that allows the exhaust system to increase power evenly throughout the RPM range. The feature that sets HMF apart from any other after-market exhaust is the sound coming from the Performance Series can be described as a deep aggressive, angry tone. Free spark arrestor with each muffler ordered!