All pictures represent actual product. Socket Cap Screws are reliable and durable and are used in many applications. With a high cylindrical head, socket cap head fasteners have a recessed driving area and offer high hold power at high torque levels. Socket head screws for use with hex or allen wrench. These screws are designed to go through a hole or nut that is pre-tapped to form a mating thread for that screw. Coarse threads are better when working with brittle materials; they are sturdier and are easier to thread and unthread compared to fine. Coarse threading also allows for thicker coatings and platings. Length of the screw is measured under the head (part of screw that penetrates fastened material). Fully threaded shanks.