4GB ( 1x 4GB Module ) DDR3 1600 MHz ( PC3-12800 ) DDR3 DIMM ( 240-Pin ) ECC UDIMM ( ECC Unbuffered DIMM ) 1.35V - DDR3 Low Voltage Compatible Equivalent for HP 733019-581, A2Z48AT, A2H31AV, 821223-081, 820077-B21, 823810-001, A2Z48AA 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