Let me tell you the history of the Penrose Kettles. The very first one (I still brew with this one) had a closed 1/2" nipple cut in half, welded on. These early kettles were made out of junked home based liquid oxygen tanks that were being scrapped out. I was able to aquire a dozen, dozen and a half of these. I sold these around St Louis. When we started making the Brewhemoths, a couple boxes of what we call "pizza pans" (flat bottoms) were found. The Penrose Kettle was back. 1/2 couplers were in use then, screw a closed coupler in, then valve. But some folks wanted to add to the inside, so a full coupler was added. Increased set up time for welding a bit, but the versatillity of the kettle went up. Downside, sticks out a bit. We can, and will put almost anything on it, or nothing at all, the price will be adjusted depending on cost and time involved. Our design idea is function over form, they may not be the prettiest thing going, but I think for the money, they are the best deal on the market!