A 563.Unless otherwise specified, the grade and style of nutfor each grade of fastener, of all surface finishes, shallbe as follows:Fastener Grade and SizeNut Grade and StyleAA, C,1⁄4to 11⁄2in.A, C, over 11⁄2to 4 in.B,1⁄4to 4 in.A, hexA, heavy hexA, heavy hexA...