ISO 4017:2014 specifies the characteristics of hexagon head screws with threads from M1,6 up to and including M64, of product grade A for threads M1,6 to M24 and nominal lengths up to and including 10d or 150 mm, whichever is the shorter, and product grade B for threads over M24 or nominal lengths over 10d or 150 mm, whichever is the shorter.