Lexx Performance Exhaust KTM 450 EXC 4-Stroke 2004-2007 Engineered to improve torque and acceleration with an increase of up to 4 horsepower on some machines.Lightweight design saves up to 3.5 lbs. over the stock exhaust. Included 46mm Race Tip for closed course competition.Includes USFA approved Quiet Core spark arrestor insert that brings sound levels down below 96db. Optional tuning exhaust tips and optional screen type Spark Arrestor are available to allow user to further tune power and sound characteristics. Constructed of lightweight 6061 T6 aluminum and durable 304 stainless steel. Limited lifetime warranty.