Carriage bolts are also called round head bolts. Carriage bolts are characterized by a square neck under the head. Their grades can be divided into 4.8, 8.8 and 10.9. The corresponding materials are low carbon steel, medium carbon steel and alloy steel. The materials of stainless steel can be divided into A2 and A4, which are the most common. The surface treatment includes oxidation blackening, electro galvanizing, hot galvanizing, passivation and baking varnish

There are also two types of carriage bolt heads, one is big round head, and the other is small round head. They are produced according to customer requirements. The size also has metric system and imperial system.