AN3H bolts have a drilled head for safety wiring. They have 10-32 UNF threads and a 3/16" diameter shank. All sizes of AN3H bolts have a 0.406 inch thread length. This thread length has been designed specifically to accommodate a full-height nut plus one AN960-10 washer. Sold individually; nuts and washers sold separately. Grip Length refers to the length of the unthreaded portion of the shank. Grip lengths are available in 1/8" increments to match the thickness of the materials being bolted together (the threaded portion should never be positioned inside the hole). If your assembly is between sizes, select the next longer bolt and use additional AN960-10 and AN960-10L washers to take up the slack. 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, AN3H-6A) 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.