4GB KIT (2 x 2GB) For HP-Compaq Z Workstation Series Z200 Z400 (4 DIMM Slots) Z400 (6 DIMM Slots). DIMM DDR3 ECC Unbuffered PC3-10600 1333MHz RAM Memory. Genuine A-Tech Brand. 4GB KIT (2 x 2GB) DIMM DDR3 ECC Unbuffered PC3-10600 1333MHz RAM Memory Genuine A-Tech Memory Lifetime Warranty Toll Free Technical Support 1-866-557-4527 Designed For HP-Compaq Z Workstation Series. (See Compatibility List Below)