Crucial 8GB Kit (4GBx2) DDR2-667MHz (PC2-5300) CL5 Fully Buffered ECC FBDIMM Server Memory CT2KIT51272AF667 / CT2CP51272AF667 Increases system performance Easy to install Premium quality memory from a trusted brand 100% Tested Limited Lifetime Warranty to use fully buffered DIMMs, your server or motherboard must use FBDIMM architecture. An FBDIMM will not fit into a standard DDR2 socket, and a DDR2 module will not fit into an FBDIMM socket