DP size
The DP is 4" all the way, it's flanged to bolt up. If the stock tail pipe is cut just where it goes to 4" behind the muffler then 2 pieces of 4" pipe ( if a premuffler is used) and clamps (use band clamps) will convert the whole system to 4" provided you have 4" muffler(s) and DP. I had installed the silent might, the premuffler, used the stock tail pipe and stock DP. The stock DP worked at stock HP. As I upped the HP a complete 4" was needed turbo back and I purchased a Pinnacle complete system. So, used mufflers and unused DP need a home. A word on size, if your not adding HP just replacing the stock muffler with a straight thru will amaze ya but be prepared for some noise. HP increases will require larger exhaust. Now start thinking intake, like that little bitty hole onto the air filter box. If ya want it to go, it's gotta suck, so it's cold air intake time.