Description AussieSpeed 4 stroke go kart muffler, This muffler is designed as a 2 piece design with inner tube to extend exhaust header pipe. The muffler has 2 mounting points to mount to header pipe with springs. Muffler is finished in a high temp paint.you are purchasing a complete muffler kit to fit a 23mm factory Briggs & Stratton World Formula header pipe muffler length 395mm id of outer tube 49mm