They are stainless steel flat washers, described in the listings as high‑strength stainless steel.

Listings describe them as multipurpose: furniture assembly, automotive repair, outdoor construction, mechanical maintenance, electrical installation, and industrial equipment fastening.

Place the flat washer between the bolt head (or nut) and the mating surface so the washer sits flat against the contact surface.

The listings recommend placing the flat washer under the bolt head or nut and, for greater stability, using it together with an anti‑loosening washer.

They have a black coated finish described as wear‑resistant and corrosion‑resistant, tolerant of high and low temperatures and less prone to rust for longer life.

Product details include a 'Dimensions (Overall):' line showing Length (L), Height (H) and Width (W), and they also list Weight and Package Quantity.

They help distribute bolt and nut load pressure, reduce surface damage and loosening, lower friction, and act as a protective layer between the fastener and the workpiece.

The listings state the black coating is wear‑resistant and corrosion‑resistant, tolerates high and low temperatures, and is less prone to rust for long‑lasting durability.