AddOn AM1333D3DRE/4G x1 HP NL797AA Compatible Factory Original 4GB DDR3-1333MHz Unbuffered ECC Dual Rank 1.5V 240-pin CL9 UDIMM

These parts are Factory Original Tier 1 modules (from either Samsung, Micron, Hynix, Infineon, etc.). You cannot buy a better module, and there is a good chance that it is an identical module you may get directly from the OEM. All ACP modules are built to meet or exceed OEM specifications, and JEDEC standards. All memory modules come with a Lifetime warranty and are 100% guaranteed compatible for the appropriate systems it is intended for.