Actually it's the stock one that came with the kit, but because of the big curve in the bottom frame of this Del Mar it kept the front wheel from turning. The exhaust stuck out too far, and wrapped around to the other side of the frame. I was tired and stumped, so I took it to a shop that's been around probably since the sixty's. He cut and welded in a 1 inch peace, so now I have a tiny expansion chamber, and a little shorter exhaust. I climbed a long steep hill today at just under half throttle,and never felt any lugging, and could have gunned it even faster, so it's got plenty of back pressure. Actually since it's a cruiser I could have tried a long pipe, with the same muffler. I'll try to get a pic, because I want to show the bracket he did for the muffler.