1.1 ,This specification2 covers a variety of carbon, alloy, and martensitic stainless steel nuts in the size range ,¹/₄ ,through 4 in. and metric M12 through M100 nominal. It also covers austenitic stainless steel nuts in the size range ,¹/₄ ,in. and M12 nominal and above. These nuts are intended for high-pressure or high-temperature service, or both. Grade substitutions without the purchaser's permission are not allowed.