Crude Neilnail Masks are intergalactic materials in Xenoblade Chronicles X. They are needed for the creation of all level 60 Skells except for the Excavator. Twelve are needed to craft an Ares 90 Skell, and six are needed to craft an Ares 70.
They can be obtained from the BLADE terminal for 210 Reward Tickets each or from the time attack mission Twin Dolls of Mystery. They can also be obtained by clearing squad missions which involve defeating Neilnails.