The Discount Strut Accessories 3/8" Lock Washers are designed to be tightened to a required torque beneath a regular fastener. They exert a spring tension that keeps the fasteners from vibrating or moving. Over time, nuts & bolts loosen from turning or slipping, but Discount Accessories's Lock Washers secure the bolt in place & prevent future loosening. Finish: EG Size: 3/8"