4GB ( 1x 4GB Module ) DDR3 1333 MHz ( PC3-10600 ) DDR3 DIMM ( 240-Pin ) ECC RDIMM ( Registered DIMM ) 1.5V - DDR3 Standard Voltage Compatible Equivalent for HP 536889-001, FX621UT, FX621AA, 500203-061, 500658-B21, 500203-561, 500203-361, 501534-001 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