Since your public profile states that you have a 1995 Civic EX, D16z6, I'll go off of that. The DX,LX, and EX for them don't have a secondary O2 sensor on the cat like the newer ones did. Just the one that goes to the exhaust manifold/header. If I remember from owning both the LX and EX, I was able to swap the cat to check the size, and they were both the same length. I thought I remember reading that on paper, the EX requires a different model cat, but is the same length physically. I got away with passing smog with a 3rd party brand that was made for 92-95 civic (non-VX) and it passed fine. I used the same cat on both LX and EX when it came time to smog to save a few bucks, and passed. But again, you don't have to worry about the second O2 sensor as there is none.