4240-01-251-9401 (D-UB1311-5M410-1)
4240-01-251-9401 is equivalent to manufacture part number 481223. It is a air line mask and is classified under Federal Supply Class 4240 (4240 - Safety and Rescue Equipment), stocked for defense, aerospace, MRO, and industrial maintenance applications. This item is cataloged in the NATO supply system under 4240 - Safety and Rescue Equipment and is available through NSN-PARTS for U.S. government MRO, and commercial procurement.