I was told that there was a little part on the catalyc converter that sticks out and goes into the piping of an exhaust, like the male part or something, so there wont be any exhuast leak. Is this true? The reason i came across this was because i have a messed up exhaust on, and the previous owner of my car instead of putting flanges on the piping he jus welded the piping to the flange of the cat. I was going to cut it off and grind it down to flange so i can bolt up my new exhaust, but i heard about that male part. I already bought a cat jus to be safe.

 

If the cat is a factory one which I doubt cause people would'nt pat $700 for a new cat than it uses flanges. Most of the aftermarket and universal cats are the same diameters on both sides so most of the time its welded on.

 

so the factory ones do have it and the aftermarket ones dont?