These are a Solid turned Cup washer, not the usual hollow stamped.
Stainless material A1
Cup washers are indented washers used with either round or countersunk head screws. These washers are designed to create a flush finish, often seen on furniture.
Stainless steel cup washers are specialized fasteners with a concave design, used to hold countersunk screws securely while providing a clean, finished appearance.
They offer superior corrosion resistance and durability, making them ideal for high-visibility or harsh environments.
To fit Screw diameter 12 gauge = 5.6mm
Washer dimensions
Inside Diameter: 7.0mm
Outside Diameter: 16.0mm
Height: 3.5mm
Top of Cup OD: 12.0mm