1 Here is the 2.25-inch U-Fit kit from Flowmaster. It's made from mandrel-bent, 16-gauge aluminized steel tubing and comes with all the necessary bends and angles you need to do the job at home. You will need to pick up a set of mufflers, a hanger kit, and possibly some tips to round out the system. Some of the sections of pipe have an end that has a larger diameter. This is so you can slip it over another piece of pipe for easy install.