Specification：Heavy hex nuts are thicker and wider than (finished) hex nuts of the same size, which makes them the strongest of comparably-graded nuts. Their additional strength comes from increased thread engagement, which is due to their thickness, and greater resistance to dilation (expansion or stretching) because of their larger width. The heavy hex nut's increased size yields a larger bearing surface and improved wrenchability. Hex is short for hexagon, which means they have six sides. They are also known as: heavy nuts. Lock washers may used with heavy hex nuts.