[Three02much]

I'm not sure on what they are actually called. One of mine, the front ones, was making noise and i took it to a muffler shop, he called it a cat. I ended up cutting one side open and removing the front ones. I live in Texas, they require emissions inspections, my car passes still. The deal inside was made out of a brittle gray material that was full of square holes, dunno if that's a cat or not, hope it helps.