Seven sizes of Grade A parallels with cross section 3/16 in x ½ in to 1½ in x 3 in and nine of Grade B parallels with cross sections 3/16 in x ½ in to 2 in x 4 in. Material, standard sizes, finish, accuracy, protection and marking.Cross References:BS 860BS 891:Part 1BS 906:Part 1BS 1133:Section 6Replaces BS 906:1940.