Although the X-tube has 2.5" tubing on both ends, it shrinks to 1 7/8" when the tubing is welded to the body. Wanted to use it to replace a resonator that tapers to 2 inches. The fact that they are narrowed down to 1 7/8 inches makes them unusable. They look like a great alternative to Magnaflow, but don't be fooled, you get what you pay for.