MacMemory Net 16GB DDR3-1066 ECC DIMM PC3-8500 DDR3 1066Mhz Kit for Apple Mac Pro (2x 8GB) 16GB DDR3-1066 MHz DIMM (2x8GB) for Mac Pro 4,1 and 5,1 Quad-Core and 8-Core All our Mac Pro DIMMs are UNREGISTERED Error-correcting Code (ECC) memory. May not mix with non-OEM, registered memory. Optimized and rigorously tested for Macs All Ramjet products are sold exclusively by the Ramjet Store