The 18-8 stainless steel hex bolt has a plain finish and an external hex drive, and meets American Society of Mechanical Engineers ASME B18.2.1 and American Society for Testing and Materials ASTM F593 specifications. The 18-8 stainless steel material provides strength and offers good corrosion resistance in many environments. The material may be slightly magnetic. The external hex drive has six flat sides that a wrench can grip to turn the screw from the side, enabling use when there is no space above the head for a driver.
Cap screws and hex bolts are threaded fasteners with thick hex-shaped heads that can be used with threaded nuts or in areas with limited clearance above the tapped (threaded) hole. Cap screws have slightly different dimensions than hex bolts and have a washer face underneath their unflanged hex head to act as a large bearing surface against the mating material.