Patented design removes old, stripped, rusted, or damaged nuts and bolts up to 85% rounded. Impact-grade chrome vanadium steel for strength and durability. Sizes: 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 13/16", 7/8", 15/16", and 1". Case features dual-hinge design for easy access.