There are three basic types of shackles. All meet or exceed U.S. Federal Specification RRC-271D, "Chains and Attachments: Welded and Weldless", and are made of alloy steel or carbon steel. They are ...

Another critical factor is the material. D ring shackles are typically made of steel, stainless steel, or aluminum. Steel shackles are the most common and affordable, but they can rust over time.