06-08 HONDA CRF450R: Big Gun Evo R Slip-On Exhaust The Big Gun Evo Racing Series was designed to deliver maximum horsepower and torque gains throughout the RPM range. Made from stainless steel tubing and an aluminum muffler canister, the Evo exhaust system is much lighter than stock units. The sleek muffler design also allows for maximum clearance to avoid your exhaust from hitting the rear brake caliper.All EVO R Series pipes come in stainless steel with a CNC-machined bracket, Race Tools packing, and spark arrestor screen. No other pipe on the market will come with these included accessories.Lighter than stock exhaust.Massive horsepower and torque gains.Hand TIG welded 304 stainless steel mid pipe construction with a brushed finish.Sleek silencer design provides maximum cle Mike has found that having the most horsepower and the lightest exhaust was not always the answer.