Security Locknut, Inc. manufactures locking fastener systems (including lock bolts, lock nuts, lock washers and customs) producing a full line of Standard, Heavy, Metric, Square and Thin/Jam pattern nuts in UNC, UNF, UNEF, Metric and British (BSW & BSF)thread pitches. Sizes range from 3/8 of an inch to 4 inches and M10 - M56.