The fittings on this one are the original fittings that were there when I bought it. They were just threaded in about halfway. I had thought the fittings had a number on them but it was the housing think of. The brass fittings are made for flared tubing. The center hole is around an 1/8", maybe a little bigger. I'd need to check the hole with a number drill. Top and bottom fittings are the same. I'm not sure now if it should have a smaller restrictor hole? Maybe its the Ford filters I saw the small restrictor fitting on?? I'll check tonight. I have some of those filters out there somewhere?