KOMPUTERBAY 8GB (4X2GB) DDR2 Certified Memory for IBM System X x3400 39M5791 DDR2 667MHz FBDIMM ECC Fully Buffered (an FBDIMM will not fit into a standard DDR2 socket, and a DDR2 module will not fit into an FBDIMM socket) Capacity: 8GB Speed: PC2-5300F 667MHz CL 5 Thermal Heatspreaders for Cooling 240-Pin FBDIMM Fully Buffered Lifetime Warranty