I have been unable to find a translation for this item. They are fragments of white polystyrene, that are added in a box (when there is enough space left in it) in order to reduce the impacts of transportation, so the item in the center of the box is not damaged.
styrofoam = polistireno https://books.google.com/books?id=f0Zunqj2fa0C&pg=PA416&lpg=PA416&dq=Styrofoam
ero = piece
eroj de polistireno = pieces of styrofoam
polistireneroj = pieces of styrofoam