04-06 KTM 450EXC: FMF Q4 Spark Arrestor Slip-On Exhaust (Aluminum) As the pioneer of quiet performance mufflers, FMF raised the bar again in 2007 with the second generation of Q series mufflers, the Q4.Built from the ground up, the Q4 is a completely new design, engineered for maximum performance while maintaining a soun The Q4 is the market leader for low sound / high performance. Less sound equals more ground.The Q4 incorporates Factory Forward Engineering to move the muffler closer - centralizing the mass for improved handling characteristics.The new Hi-Flo formed end cap reduces weight and is less prone to damage.The Q4 has an a Not intended for street use.