Teeth on the outside edge of the washer bite into the screw head and joint for a tight grip. Use with fasteners that have heads large enough to make contact with the teeth, such as pan, button, and binding head screws. Manufactured from 410 Series Martensitic Stainless Steel. 410 is a stainless alloy that has a higher hardness than 18-8 Stainless Steel but is less corrosion resistant than 18-8 and will be magnetic.