Use H172b for the large end of H-Shackles and H172sb for the small end. Unlike S-hooks they can be used multiple times. They are also much easier to install then S-hooks and much stronger. Some cities and parks are requiring their use instead of S-hooks. . The shackle is 212 HBS and the bolt is 176 HBS. The hardness of the bolt in the long needle hardness HRC29 / short needle hardness HRC31. 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 6800 lbs.