The 1/2"-13TPI x 2.00" High Head Hex Bolt was mailed to you earlier today for exact replacement.  Please send back along with my order for the 20, 5/16" - 18TPI x 1.00" High Head Hex Bolts (NUT310).  The tracking number for the package is - 9500 1143 9418 0104 4827 09  Thank you for your help with this order.  Terry Wiegand, 210 East Avenue F, South Hutchinson, Kansas, 67505-2038