661-5005 1066 UDimm, 4 GB, DDR3 ECC - Early 2009 A1289 Mac Pro NB-2217W This is 4GB DDR3 PC3-8500 DIMM RAM upgrade for the Mac Pro. This is for PC3-8500 DDR3 Machines. These are DIMM chips and not SODIMM chips used in MacBooks and iMacs. Apple part number: 661-5005