Crucial 4GB Single DDR3-1866 ECC UDIMM 1.5V Memory For Mac Pro Systems (Late 2013) CT4G3W186DM Compatible with Mac Pro workstations Increases Mac Pro system performance Runs at 1866MHz-the fastest mainstream DDR3 ECC UDIMM and RDIMM speed currently available Lead- and halogen-free Easy to install Every module extensively tested at the component and module level for complete functionality Limited lifetime warranty Trusted by enthusiasts of Mac systems