You do not need to buy the entire FMF exhaust system, however, the pipes and silencers are designed to work better as a unit. Each silencer and exhaust pipe are available separately and can be interchanged to a degree, or used with stock components, as FMF uses the same spacing as stock. For machines like Yamaha’s Banshee, there is no real advantage to not replacing the entire exhaust system, as Yamaha’s stock setup is heavy and robs the machine of a lot of power. If, for example, you want to buy a 4.1 muffler now, you can buy it as a slip-on system and then add the PowerBomb or MegaBomb later if you like.