Diameter: 20mm
Diameter 2: 34mm
Thickness: 4mm
Material: Steel
Finish: Black Phosphate
Hardness: Class 10
Style: Medium Split
Type: Lock Washer
Specifications: DIN 127
Application: Nuts and Bolts

Box of 157.

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