This standard sets out minimum requirements for serially produced lightweight refillable gas cylinders having a water capacity exceeding 20 L but not exceeding 1000 L. The cylinders are intended only for the on-board storage of high pressure compressed natural gas as a fuel for automotive vehicles to which the cylinders are to be fixed. Cylinders may be of any steel, aluminium or non-metallic material, design or method of manufacture suitable for the specified service conditions. This standard does not cover metal liners or cylinders of stainless steels or of welded construction.