51404127-250 is a 15 Slot HPMM/IOP conformally coated chassis. An HPMM card file and IOP card file differ only in the application. Electrically, their backplanes are the same.

The non-CE Compliant card file models can be designated as an HPMM card file or an IOP card file by either installing an HPMM card set in the the two left-most card slots or installing IOP cards. This card file replaces the 51404127-150 card file.