Cap screws or hex socket screws and bolts are fairly vulnerable to rounding out, partiularly stainless fasteners. Countersunk hex sockets screws and button heads are an absolute nightmare if they're over tightened, because the hex socket is fairlt small compared with the screw diameter. When we ere offered this product to test we were fairly sceptical, but we would not let the rep have back the sample once we had tried it! For a tool set that only costs a couple of pints of beer, it is amazing.

It uses standard 1/4" screwdriver bit drivers and covers 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm and 6mm heads.