Synthetic round, grommet or endless slings are stronger and even lighter than other slings given their rated capacity.
There are two reasons for this. Not weaving the synthetic fibers, but instead, forming a loop of loose fibers that nest together without overlapping, eliminates cutting of internal fibers. Endless slings are inherently twice as strong when used in vertical and basket hitches as compared to their single legged counterparts. Round slings are covered with a non-load bearing sleeve which protects the loops of loose fibers.
Some theatrical round slings, identified by a black sleeve, take this idea one step further by replacing fibers with steel wires that would normally be used to make wire rope.
Manufacturers, like Lift-it, are making round sling assemblies with hardware already included. They may add a hook or link to a single sling or make multi-leg bridles with hooks and links. In order to accomplish this, slings must be manufactured around the hardware.
Our Rigging Equipment Inspector training program includes inspection of synthetic rope slings.