AN9 bolts have a 9/16-18 thread with 0.9063 inch thread length (just long enough for an AN365 locknut and an AN960-916 flat washer, each sold separately). The Grip Length refers to the unthreaded portion of the shank. Add AN960-916 and AN960-916L flat washers (sold separately) to fine-tune the grip length to match the thickness of materials being bolted together. Sold individually; nuts and washers sold separately. Torque AN9 bolts to 67-83 lb-ft with AN365 or AN310 full-height nuts. Torque them to 40-50 lb-ft with AN364 or MS21042 half-height nuts. 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, AN9-37A) indicates an undrilled shank for use with a self-locking nut. UHL: Under Head Length (also known as Full Shank Length or Overall Length not including bolt head) AN bolt nomenclature can be confusing. Please take a look at our page on Identifying AN Bolt Sizes.