1/4-20 Screw size. 1/2″ Drill size. 100/box. One EMC Setting tool (EST) included with every 100 machine screw lead anchors. Sturdy expansion anchor designed with a lead housing that provides the maximum of expansion in irregular holes and a zinc, rustproof alloy threaded metal cone for strength in holding the screw. Best suited for solid masonry. Setting tool included in each box.