These shackles take the place of S-hooks and need the wrench, H175, 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 ½” across and the larger opening is ¾”. 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. Tensile strength 6800 lbs.