diameter of this plug in the middle of the plug

89-93 Big Twin

Fits: > WLC/BT/Servi models

84-98 FLHR

Physically also fits 36-40 bikes

SUPERTRAPP, INTERNAL DISC 4" FATSHOTS SLIP-ON MUFFLERS kedjor och drev diameter of this plug inChrome. Mufflers are 3. 5" diameter and flare out to 4" at the Slash Cut end. Overall length is 16", making it a short aggressive large volume muffler. With the 12 included 4" diffuser discs per muffler SuperTrapp measured a 15% HP and 12% torque gain. With 6 discs per muffler this system is sound compliant in the USA with 86dB at idle, as quiet as stock but more powerful. Fits: > 06 17 V Rod VRSCDX Night Rod, VRSCR Street Rod CHROME MUFFLER