Car Chemistry 3DI25R CC Inserts-Insert 3 Disk Mufflers Fits 2.5 in. Dia. Pipe CC Inserts-Insert 3 Disk Mufflers 2.5" Diameter 1/pkg. CC Inserts; Insert 3 Disk Mufflers Collector Insert Muffler Or Slips In Pipe Reduces Internal Resonance