4GB ( 1x 4GB Module ) DDR3 1600 MHz ( PC3-12800 ) DDR3 DIMM ( 240-Pin ) ECC RDIMM ( Registered DIMM ) 1.5V - DDR3 Standard Voltage Compatible Equivalent for HP 676811-001, 676331-B21, 647895-B21, 647648-171, 647873-B21, 647895-B212, 664689-001, 687459-001, A2Z49AT, 647648-571 High performance Memory RAM upgrade designed for Server/Workstation Systems All modules undergo quality assurance testing to ensure dependable and reliable performance Please verify the supported memory (RAM) specifications of your system prior to purchase to ensure compatibility A-Tech provides a Lifetime Warranty for all orders & offers complimentary United States based Tech Support before, during, & after your purchase