#10 Lockwasher Stainless Steel with External Teeth
410 stainless steel for strength and durability.
External tooth lock washers create a ratchet action by biting into the nut or screw head and the surface it contacts.
When used under a screw or bolt head, external tooth washers require a large head, such as a pan or round head, so that the washer teeth can make contact with the head.
Since the teeth are on the largest radius, which results in greater twisting resistance, this type of washer is preferred when the greatest locking power is desired.