How to Upgrade the iMac 27-inch Retina 5K (2014-2015)
iMac with Retina display review: best in class, but not everybody needs one | Engadget
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 RAM at Amazon.com