Grab Screws are threaded the full length and have a drive recess fully within the shaft of the screw. They have metric thread (25.4mm equal to 1 inch). Hexagon socket drive screws have a hexagon shaped recess in the head and are driven with hex-tools. These screws are ideal for precision work with close tolerances and applications needing a well tooled appearance. They are frequently used to fasten pulleys to a shaft