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, image shown is a 2" bit.