These shackles take the place of S-hooks and need the wrench, PG176P, to open and close. This head makes removal, because of vandalism, more difficult. The overall length is 3 5/16″. The bolts are 3/8″ diameter. The inside of the smaller opening is ¬Ω” across and the larger opening is ®”. 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. Use with our swing hangers and chain. The shackle is 212 HBS and the bolt is 176 HBS. The hardness of thebolt 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.