What are the advantages of using the FSW head with retractable pin?

The use of the FSW head with retractable pin offers the advantage of not leaving an exit hole unlike standard welding heads. As its name indicates, the pin retracts at the end of the weld. It allows to directly close the hole appearing at the end of the weld.
The use of the FSW head with retractable pin avoids additional handling to fill the weld exit hole. This absence of exit hole is particularly required in aerospace applications: floor, fuselage etc.