Applies to lightweight seamless cylinders having a water capacity exceeding 4 fl oz but not exceeding 1500 lb. It specifies material requirements, including composition of steel, for three alloys, namely manganese-molybdenum, chromium-molybdenum, and nickel-chromium-molybdenum and requirements related to manufacture, including heat treatment. It sets out the design formula for calculating minimum thickness of wall and end, and gives the range of tests including tensile, bend and notched bar impact tests, and a hydrostatic pressure test on the finished cylinder. Marking and delivery requirements are also specified.