AN6 Hex Head Airframe Bolts feature a 3/8-24 tread size and come in either drilled or undrilled shank versions. The drilled shank version is designed for a 1/16 in. diameter cotter pin. The undrilled shank is designed for use with a self locking nut. In addition, part numbers that contain an 'H' in place of the '-' feature a drilled head for a safety wire.