Hey Frank, it's a 1/2" barb and a 1/2" NPT. I probably could have done 1/2" barb with 3/8" NPT as well. I put it on the left side of the filler neck (front side) at about the 10:00 position if you are looking at the gas cap. The barb points downward and the hose then goes over to the side of the tank. I'm not proud of the welding work on the bung! I had really bad shielding issues, partly because my argon tank ran out and it took me a second to figure it out, and partly because I had a large gap to fill where the bung meets the tube and I think that was giving me shielding issues as well. I back purged it and that seemed to resolve the issue.