Square M-F Lock Nuts. Hot dip galvanized. Should always be used to complete a static-proof installation. Used with a regular nut to form a solid unit which cannot loosen. Turns on the bolt with a free fit.When it touches the nut, it takes 1/2 to 3/4 of a turn to flatten the concave surface bonding it to the thread. Bolt Size: 5/8, Width In.: 1, Thickness, In.: 3/8, Std. Pkg.: 800, Wt., Lbs./100: 4.3