Stainless steel carriage bolts are available in both inch and metric sizes. Carriage Bolt Resources Round Head, Square Neck Carriage Bolts Round Head, Short Neck Carriage Bolts Round Head, Ribbed Neck Carriage Bolts Fin Neck Carriage Bolts Flat Head, Square Neck Carriage Bolts Nut Compatibility Chart Bolt Grade Markings & Bolt Strength Chart