This gives you great grip and control when stating nuts or bolts in awkward locations when you have oily hands. The design fits 3/8" square drive and is a snug fit so the socket does not fall off or wobble when the socket is fitted. The deep grooves enable you to run nuts a bolts of, or on, by hand in areas where a ratchet or spanner is hard to use. Really useful workshop addition. This made fitting a replacement fuel pump on a series landrover so much easier.