4GB EUDIMM Memory for HP Z400 Workstation DDR3L-1600 by Nemix Ram - Newegg.com
4GB RAM Memory Upgrade for HP Workstation Z400 PC3-10600E DDR3 1333MHz 2Rx8 ECC Unbuffered UB DIMM Module (MemoryMasters) at Amazon.com
Memory for a HP/HPE - Workstation Z400 - Kingston Technology
12GB KIT (6 x 2GB) for HP-Compaq Z Workstation Series Z400 (6 DIMM Slots). DIMM DDR3 ECC Unbuffered PC3-10600E 1333MHz Server Ram Memory. Genuine A-Tech Brand. at Amazon.com