16GB Memory RAM (2 x 8GB) for iMac "Core i5" 2.7 27-Inch (Mid-2011) MC813LL/A Memory Size: 16GB Kit (2 x 8GB) *There are two (2) 8GB DDR3 memory modules in this kit Memory Type: DDR3 SDRAM Number of Pins: 204 Memory Speed: PC3-10600 DDR3-1333 (1333MHz) LIFETIME WARRANTY and free Tech Support