ISO 5003:2016 specifies the terms and definitions, information to be supplied by the purchaser, tolerances for dimensions, length, technical requirements, inspection rules, identification, certification, and a quality assurance system for as-rolled and heat-treated steel rails for railways.

ISO 5003:2016 specifies flat bottom (vignole) railway rails with linear mass of 43 kg/m and above, for conventional and high-speed railway track usage.

There are 19 pearlitic steel grades specified, covering a 200 HBW to 400 HBW hardness range and including "non-heat-treated" carbon manganese steels, "non-heat-treated" alloy steels, "heat-treated" carbon manganese, and "heat-treated" low alloy steels.