Scuba Diving Tanks. Common Cylinder Sizes that we stock are Steel HP 80, Steel 100, Steel 120, Steel 130 and Some Aluminum Tanks for Stage Decompression such as Alu 30, Alu 40 and 6 Cu Ft Alu Pony Tanks for Drysuit Inflation Kits. Faber, Xs Scuba, are our major suppliers.