Apex 1/4'' drive socket head (Hex-Allen) hex power drive bits, SAE from Apex Fastener Tools. Socket head (Hex-Allen) bits from Apex Fastener Tools formally Cooper Tools. The socket head (Hex-Allen) bit is one of the most common screw drives in not only the aviation industry but the automotive repair, technology, and heavy industry sectors. The Apex brand has always stood for quality design and is constructed to last longer than cheaper alternatives. Note, that the image shown is a 2" bit.