Carriage Bolt, Fully Threaded, Measurement System: Imperial, 1/4-20 Thread, 3/4 in Length Under Head, Low Carbon Steel, A Grade, Zinc CR+3, 0.594 in Diameter Head, 0.156 in Neck, Square Neck, 60000 psi Tensile Strength, 0.26 in Drive, UNC Thread, Square Drive, B70 to B100 Hardness, Material Specification: ASTM A307, Round Head