Iron Man Mask 50: Infinity Edition Extension Set of the Marvel Cinematic Universe and Avengers: Infinity War

An extension set is a collection of accessories that were a part of a DX release but not part of the original release of the Nendoroid.  Occasionally, a Nendoroid that had only a standard release will later be released with a DX option.  When this occurs GSC will also sell an "extension set" so that those who have already purchased the original/standard release are able to get the additional parts that were only available with the DX rerelease.  Extension sets are not made when a Nendoroid has a DX and standard release at the same time.