OTC 4794 Safety Wire Drill Guide Set, SAE and Metric Set Perfect way to drill those nuts and bolts for use with safety wires without breaking the drill bit These guide, align and support the hex head or the bolt threads The hex fixture fits nuts and bolt heads that measure up to 1-1/4 inch SAE fixture bar is threaded for 1/4 inch, 5/16 inch, 3/8 inch and 7/16 inch bolts Metric fixture bar covers M6, M8, M10, and M12 sizes