Dynamic Drive Hexagon Sockets - Metric Metric square drive sockets are manufactured from British alloy steel, with a bright nickel and chrome plated finish to BS 1224: 1970, service condition No. 1. All sockets have a ball retaining groove on each face of the square drive to ensure a positive fit to accessories. All dimensions conform to BS 4006: 1987. All metric sockets are machined with a double band of knurling for ease of identification. Made from Vanadium-extra alloy with a nickel and chrome-plated fine-polished finish.