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: 3/8, Width In.: 5/8, Thickness, In.: 1/4, Std. Pkg.: 3000, Wt., Lbs./100: 1.2