Flat Washers are used to increase the surface area of fasteners, in order to evenly distribute the force applied when tightening them to a surface. They are also used to prevent loosening due to vibration, to stop the bolt or screw from pulling through, and act as spacers. They are manufactured from steel and zinc-plated and are manufactured to ASME B18.21.1 standard.Type: Flat WasherSize: 1/4(100 Pack), 3/8 (100 Pack), or 1/2 (50 Pack) Material: Unhardened Carbon SteelFinish: Zinc PlatedROHS Compliant