16GB Total memory using 4pc of4GB PC2-3200 DDR2-400 Dual-Rank Registered ECC DIMM.Lifetime warranty for exchange.We don't use Generic modules to avoid incompatibility issues.Guaranteed to work or you get all of your money back including shipping.IF YOU NEED ECC REG SINGLE RANK PLEASE EMAIL US FeaturesCompatible with Dell PowerEdge 1850First DIMM may be populated singularly, additional memory must be populated in pairs. This chipset supports a maximum of 8 ranks.