1/4" x 1/2" x 39/64" 18-8 Stainless External Tooth Lock Washers (20 pcs.)

Diameter: 1/4"
Diameter 2: 1/2"
Thickness: 1/16"
Material: Stainless Steel
Hardness: 18-8
Nominal Size: #14
Style: External Tooth
Type: Lock Washer
Application: Round|pan|or binding head
Diameter 3: 23/64"

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.