Hillman 1/4 in. -20 in. X 3 in. Internal Hex Socket Cap-Head Cap Screw (6-Pack)

Socket cap screws are very common in industrial applications. A cap screw is a fastener for machine parts, threaded along the whole length of its shank and held by threads tapped in the hole in which it is screwed. These screws provide high-torque capability and the drive system is a hexagon-shaped hole.