Full Details from Amazon.com : http://www.amazon.com/gp/product/B00JIJU6QW?tag=onigi-20Transcend 32 GB DDR3 1600 SO-DIMM 2Rx8 TS32GJMA524H (8GB x 4)For iMac 27 Mid 2011-Late 2012 SO DIMM 512Mx8 bit 1600 Mbps 15V Timing 11-11-11