Supertrapp 128-65117 SE Series Slip-On Exhaust SE Series Slip-Ons, also commonly known as the old H-D Performance II Muffler, are SAE-J2825 sound compliant.Expertly finished and chrome-plated.Champion of numerous magazine shootouts with a 10 - 12% HP gain.Steady, tough, low rumble at 3dB over stock.Co However, utilizing SuperTrapp&#39;s optional, replacement core (sold separately) with the SE Series then allows your muffler to become serviceable by having the ability to be rebuilt and repacked. Sound test data on 2010 and up model-specific slip-ons was achieved using the O.E.M. CAT-equipped headpipe. Use of these mufflers on headpipe with the CAT removed or True Duals will result in substantially louder results.