AN5 Bolts -- Undrilled Head
AN5 bolts have 5/16-24 UNF threads with 0.531 inch thread length.
A or no A? AN bolts were originally designed to be used with a castle nut and cotter pin, so the base part number indicates a drilled shank. The addition of an "A" at the end (for example, AN5-13A) indicates an undrilled head and an undrilled shank for use with a self-locking nut.
AN bolt nomenclature can be confusing. Please take a look at our page on Identifying AN Bolt Sizes.