Washers without chamfer DIN 125-1-A / ISO 7089-aluminium 13

Aluminum is a silvery-white light metal with one third the density of steel. In materials engineering, “aluminum” refers to all materials based on the element aluminum. This includes pure aluminum (at least 99.0 % Al), ultra-pure aluminum (at least 99.7 % Al) and, in particular, aluminum alloys, which have strengths comparable to steel. Aluminum alloys are divided into wrought alloys and cast alloys depending on how they are produced.

The term plain indicates a completely untreated, merely oiled, smooth surface for all DIN and ISO screws such as wood screws, hexagon head screws, threaded rods, nuts and many types of washers.