These are all O2 E cylinders repurposed for Scuba and have been hydro tested and have been given the + rating and starred which allows for ten years between tests. They are simply fun to build.....takes about 30-40 hours to do all the work. I really like these. But yes they are smaller and collectively they hold about 70 cubic feet of air.
First dives? 1967 and I never lost the fever.