Also known as alignment washers, these two-piece washer sets compensate for misaligned parts and uneven surfaces. The top washer sits and swivels in the hollow of the bottom washer.
This magnetic material is the most common choice for everyday fastening applications. Black oxide gives the washers a black finish.
Stainless steel has a naturally corrosion-resistant surface that continues to protect the material from environmental contaminants even if scratched.