ISO 8673:2012 specifies the geometry of hexagon nuts with nominal thread diameter from 8 mm up to and including 64 mm and the mechanical properties of hexagon regular nuts (style 1) with metric fine pitch thread in product grade A for nominal thread diameters 8 mm less than or equal to D less than or equal to 16 mm and in product grade B for nominal diameters 16 mm less than D less than or equal to 39 mm.