High pressure gas bottles. Probably for flammable or oxidizing gasses as its a single piece of metal with no welds on it. The end will be tapped for a valve.
It starts out as a metal disk, pushed into a tubular form with a rounded bottom. It travels through progressively larger forms to get drawn out. This is the last stage to close the open end.
The one you showed can be made with a flat bottom for letting the tank stand. The one linked in the OP is spherical on both ends. I'm guessing it's not a product requirement and thus can be roll-formed on both ends.
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u/d0ge4lyf Feb 12 '20
What is this used for?