ATHS250-12 Hi-Lok Installation Socket 1/4” 12PT Socket with Set Screw Retainer. These anti-FOD sockets are manufactured to fit conventional square drives. Hi-Lok® installation sockets feature a generous through-hole to enable the use of hex keys when necessary for Hi-Lok®, Hi-Lite®, and Hi-Tigue® installations. A set screw is provided to positively retain the sockets onto the square drives as an anti-FOD measure.