The Vibration Proof Lock Washer, designed for 1/2" (12MM) bolts, features an outer diameter of 49/64" and is made from through-hardened carbon steel with a hardness rating of 465 HVI. This washer effectively prevents loosening due to vibrations, making it ideal for automotive and industrial applications where reliability is critical. Supplied in a box of 20 (10 pairs), it offers durability and performance for various fastening needs.