| 摘要 |
A screw driver bit includes four side walls arranged in a square cross section substantially throughout a length thereof which taper inwardly towards one another towards the apex of the bit such that the bit is arranged to mate with each of a plurality of different standard size Robertson type sockets. A corresponding socket also includes four side walls arranged in a square cross section throughout the length thereof as the side walls taper inwardly towards the apex such that the socket is arranged to mate with the corresponding bit and with each of a plurality of different standard size Robertson type screwdriver bits.
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