64GB KIT (8 x 8GB) For HP-Compaq Workstation Series Z420 (ECC Registered). DIMM DDR3 ECC Registered PC3-12800 1600MHz Dual Rank RAM Memory. Genuine A-Tech Brand. 64GB KIT (8 x 8GB) DIMM DDR3 ECC Registered PC3-12800 1600MHz Dual Rank RAM Memory Genuine A-Tech Memory Lifetime Warranty Toll Free Technical Support 1-866-557-4527 Designed For HP-Compaq Workstation Series. (See Compatibility List Below)