BBI Carriage Bolt, Passivated, Measurement System: Imperial, 1/4-20 Thread, 1 in Length Under Head, Stainless Steel, A2 (18-8) Grade, 0.594 in Diameter Head, 0.156 in Neck, Square Neck, 150000 psi Tensile Strength, 0.26 in Drive, UNC Thread, Square Drive, B95/C32 Hardness, Material Specification: ASTM F593, Round Head