Melco Ta 2 A/F Box Spanner 3/8 X 7/16 X 4 in. Box spanners are thinner than a socket & are much longer so that they can be used to loosen or tighten bolts & nuts in narrow recesses, meaning that they are often used in plumbing maintenance & automotive repair. This tubular box spanner is made from bright plated steel & able to accommodate a tommy bar. Size 3/8 x 7/16 in. AF Double Ended. Length: 4 in. 100 mm.