#10 x 3/16" x 21/64" Black Chrome Plated Grade 2 Steel Lock Washers

Diameter: 3/16"
Diameter 2: 21/64"
Thickness: 3/64"
Material: Steel
Finish: Black Chrome
Hardness: Grade 2
Nominal Size: 3/16" (#10)
Style: Medium Split
Type: Lock Washer

Box of 20.

The purpose for a lock washer is to prevent threaded fasteners from loosening by creating friction between the fastener and the mounting surface.