BBI Carriage Bolt, Fully Threaded, Measurement System: Imperial, 1/2-13 Thread, 5-1/2 in Length Under Head, Low Carbon Steel, A Grade, Zinc CR+3, 1.094 in Diameter Head, 0.281 in Neck, Square Neck, 60000 psi Tensile Strength, 0.515 in Drive, UNC Thread, Square Drive, B70 to B100 Hardness, Material Specification: ASTM A307, Round Head