Icaro Wire Stop (Wire half moon.)
This small plastic part fits against the stop ferrule in continuous front to rear rigging that is often fitted to Icaro and A-I-R hang gliders.
In conjuntion with the stop ferrule on the lower front to rear rigging iIt prevents the bottom of the upright from moving along the wire.
When worn the aluminum section of the upright tends to dig into the plastic fitting and the wires thus move slightly in the fitting. The effect of this is sometimes first noticed by the pilot as looser front to rear rigging or a different exit point of the wire from the lower plastic fitting on the upright.
They are simple to change.