This Sun 511-1152 compatible 4GB DDR2-667MHz dual rank fully buffered ECC 1.8V 240-pin CL5 factory original FBDIMM is 100% guaranteed to be compatible with your system and to work right the first time. All of the server memory is built to strict JEDEC standards at one of the tier 1 facilities (Samsung, Micron, or Hynix). The products are also guaranteed by federal law to not affect or void OEM warranties.