With the original design hidden weld titanium coupling, the lugs press into the tube and are then welded in place. Once the lugs are welded to the tube, beauty rings, which were previously pressed on the tubes, are pressed back toward the coupling to cover the welds. The beauty ring on the ring lug side of the coupling (the side that retains the nut) not only covers the weld but it provides a shoulder to prevent the nut from sliding down the tube which could scratch it. The ring also keeps debris from getting under the nut. When the coupling is screwed together, only the nut and the two beauty rings are visible, the welds are hidden. The advantage to this coupling is that the welds don't show. The disadvantage is that it's harder to install than the visible weld coupling and it's a few grams heavier.