Package dimensions: 11x19x3cm. 3/8” sq. Drive for use with hand, air & impact wrenches . Hexagonal flats for use with flat wrench, pliers & adjustable wrench, sockets. Chrome molybdenum. Sizes: 1/4” (6mm) 5/16” (8mm) 3/8” (9.5mm) 7/16” (11mm) 1/2” (12.7mm)