07-09 YAMAHA YZ450F: Pro Circuit T-4 Head Pipe (Stainless Steel) The hand-built stainless steel Head Pipe allows for one of the finest bolt-on modifications that you can add to your motorcycle or ATV. The unique design will enhance low to mid RPM power, making it the perfect choice for upgrading your stock system.Built using 304 stainless steel designed for maximum durability, corrosion resistance and style.Replaces stock head pipe.Will fit the O.E.M. or Pro Circuit Slip-On.