If you're talking about the long screw that holds the two pieces of the muffler together, don't buy a new one! It'll just break like the old one. Just go to the hardware store, get some 6-32 threaded rod and two nylon-insert lock nuts. Drill out the front and back of the muffler for the threaded rod. Go flying! Just be thankful you didn't lose any parts while in the air.