8GB Kit (4GBx2) Upgrade for a Apple iMac 3.1GHz Intel Core i5 (27-inch - DDR3) Mid 2011 System (DDR3 PC3-10600, NON-ECC, ) 204-pin SODIMM DDR3-1333 DDR3 PC3-10600 Unbuffered, NON-ECC, DDR3-1333, 1.5V, 512Meg x 64 The only brand of memory upgrade available directly from a DRAM manufacturer, tested to meet the most stringent industry specifications Install it yourself in about 15 minutes. The same top-quality memory that the worlds largest computer manufacturers install in the systems they sell