Prime-Line 400 Series 3/8 in. Stainless Steel External Tooth Lock Washers (10-Pack)

External tooth lock washers feature teeth that help to prevent loosening of a nut or bolt by digging into the surface. For maximum holding power, use one between the surface and the bolt head, and use another one between the surface and the nut. The bolt head should be at least the same size as the total diameter of the lock washer. Lock washers are great for use in cases where the bolt may be subject to vibration.