More descriptively, a Screw Pin Anchor Shackle, an attachment device used in stage rigging.
Sized by the diameter of the thinnest part, at the bell (AKA the bow), ranges from 3/16" (WLL: 1/3 ton) to 2 1/2" (WLL: 55 tons). For more, see http://www.thecrosbygroup.com/products/shackles/screw-pin/carbon/crosby-209-carbon-screw-pin-theatrical-shackles/ . The most common size for arena rigging is 1/2", with 5/8" used for 2T points.
Sometimes abbrev. as SPAS. There are other types of shackles, but above is by far the most common in our industry.