Disc-only models depend only upon the discs to provide less noise reduction and are ideal for limited space applications such as midgets and sprint cars. The series 544 models use 5" diffuser discs. The SuperTrapp uses a patented radial diffuser system. a series of discs with a precise gap form an exhaust outlet. By adding or subtracting discs, you can virtually wave tune your engine and carburetion. You can increase or decrease the exhaust outlet size; adding discs opens the system and removing them reduces it. The fewer the discs, the quieter the system; the more discs, the nosier it becomes. SuperTrapp dispenses exhaust gases radially rather than straight out, it is greatly effective in reducing noise levels. This opening and closing of the exhaust exit is very important to tuning. Allowing you to adjust your powerband, according to the type of track you are running. Remove discs to decrease the exhaust opening and increase back pressure. This decreases the powerband to give you more low-end torque. Decreases the exhaust tone. Enriches the carburetion. Add discs to increase the exhaust opening and reduce back pressure. This increases the powerband to give you more top- end. Increases the exhaust tone. Leans out the carburetion. NOTE: SuperTrapp Disc Only and Glasspack models have almost identical flow characteristics. Noise level is a primary concern when choosing between the glass pack and disc only mufflers.Pit Stop USA offers Supertrapp Disc-Only Diffuser Assembly - Fits 3-1/2" Diameter Pipe 544-3503 at low everyday prices. Be sure to check out all of our products from Supertrapp including Supertrapp Model 544 Disc Only Mufflers and Supertrapp Sprint Car Mufflers.