Sunex 218fp 1/2-Inch Drive 9/16-Inch Female Plug Socket Forged from the finest chrome molybdenum alloy steel-the best choice for strength and durability Radius corner design-to extend the life of fasteners The design drives the side of the fastener instead of the corner Provides increased strength, but also avoids rounding of rusted or damaged fasteners 1/2-Inch drive, 9/16-Inch female plug socket