Ramjet 16GB DDR3-1066 ECC DIMM PC3-8500 DDR3 1066Mhz Kit for Apple Mac Pro (4x 4GB) All Ramjet products are sold exclusively by the Ramjet Store. All our Mac Pro DIMMs are UNREGISTERED Error-correcting Code (ECC) memory. May not mix with non-OEM, registered memory. MacMemory Net has NOT authorized any Amazon Sellers to list the MacMemory Net brand for resale. 16GB DDR3-1066 MHz DIMM (4x4GB) for Mac Pro 4,1 and 5,1 Quad-Core and 8-Core Optimized and rigorously tested for Macs