Internal/External Tooth Lock Washer, Steel, Zinc Plated Finish, Titan Fasteners, Mfr#: BHA66

#6 combination internal/external tooth lock washer - steel - zinc - pkg of 100 combination internal/external tooth lock washers provide dual benefits. The internal teeth lock into bolt heads or nuts to prevent backoff rotation, which works best with smaller head screws, such as fillister heads. The external teeth secure bolt heads or nuts to increase the bearing area and offer greater hardness so that the nut or bolt can be rotated without distortion of the bearing surface.