#4 x 7/64" x 17/64" 18-8 Stainless External Tooth Lock Washers LWSS-054 (50 pcs.)

Diameter: 7/64"
Diameter 2: 17/64"
Thickness: 1/32"
Material: Stainless Steel
Hardness: 18-8
Nominal Size: #4
Style: External Tooth
Type: Lock Washer
Application: Round|pan|or binding head
Diameter 3: 13/64"

Box of 50.

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