No lock washer needed - nylon insert prevents nut from self-turning * Great for high-vibration applications * Steel with zinc finish for superior rust resistance; includes resealable organizer case * Six of most-common SAE sizes: #10 x 24 TPI, 1/4 x 20, 1/4 x 28, 5/16 x 18, 3/8 x 16, 1/2" x 13 * Excellent value - 150 quality lock-nuts for less than a dime each!