A 16 ounce beer can, cut cleanly around the ring at the top with a can opener, is an exact fit around my muffler. Two together extend the muffler several inches and cut down on the sound- not greatly but maybe 10-15 percent. The aluminum cuts fairly easily- snips on the bottom where the can opener won't fit! Some radiator hose clamps hold them on- I've only got one now, but taped over the whole thing- it isn't real pretty, but my muffler wasn't before- and the end cap had vibrated off. I drilled some smaller holes in the end of the bottom one. Plus it's all a great heat sheild to keep from getting burned! And definitely a Db or two quieter. I don't think you can get busted for carrying empty containers if the top and bottom has been cut off! if you're under age, this is the time of year they're laying in the ditches. .