Adamanta 16GB (2x8GB) Apple Memory Upgrade DDR3L 1600MHz SODIMM Compatible for iMac (Mid 2011, Late 2012, Early/Late 2013, Late 2014, Mid 2015), MacBook Pro (Early/Late 2011, Mid 2012), Mac Mini at Amazon.com
32GB 4X8GB NEMIX RAM Memory for Apple iMac Mid & Late 2011 - Newegg.com
21.5-inch or 27-inch iMac (Mid 2011) Memory Installation Video - YouTube