Nuts and Washers Selector
Spring Washer, these are a thin circular plate with a central hole but have a split in and bent into a helical shape. They are used to increase the force between the male and female thread increasing friction and therefore resistance to rotation, hence they are sometimes referred to as lock washers.
BZP - Bright Zinc Plated - A 3 micron plating is applied to the steel to give a shiny finish. Although it does afford some protection this is best suited to an indoor use.