Well we used to make those rings and put the fins on, rivet them on, and the bombs, the, the, the  the rings was  erm  seamlessly weld on a  a welder that you  two w wheels which were electrically driven  and the power was put through them and, and you overlap the two seams like that, and it, as the wheels went round it'd weld them straight along, they was about eight inches deep  seam weld them right down.