Melco TM9 Metric Box Spanner 12 x 13mm x 100mm (4in) Double ended 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 12 x 13mm Length 100mm (4 in)