1/2-13 Carriage Bolts have a 1/2 square shoulder below a 1-1/16 diameter round head. The fastener length is measured under the head including the square shoulder. Carriage Bolts up 6" long are typically fully threaded. Carriage Bolts longer than 6 inches usually have 6 inch of thread. 18-8 Stainless Steel for general construction, industrial and marine applications.