This is a standard 5/16″ x 3″ S-hook. These can be used with all of our chains. Our commercial quality S-hooks are designed to fasten chain to swing hangers and swing seats to help prevent binding. They are plated to resist rust. S-hooks that are not bought from a playground manufacturer do not have the quality control and have been known to break with the first “swinger”. This product should last 2 years in harsh conditions and up to 5 years in optimal conditions. Some conditions may require replacement sooner. Tensile strength 1126 lbs.