Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
Mac RAM Upgrade, Best iMac Memory Upgrade – Best Reviews
NEMIX RAM 16GB Kit (2x8GB Upgrade) DDR3-1600 SODIMM PC3-12800 for Apple MacBook Pro Mid 2012 / iMac Late 2012 / iMac 2013, Late 2014, Mid 2015, Mac Mini Late 2012 at Amazon.com
CMS 16GB (2X8GB) DDR3 12800 1600MHz Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I5 3.4 27-Inch (Late 2013) Me089Ll/A - A7 at Amazon.com
Late 2013 iMac review: Faster than before, but the gains over previous models are modest | Macworld
8GB 2x4GB DDR3-1600 RAM iMac 27” Late 2013 Memory Direct Takeoff Not Aftermarket | eBay
CMS 32GB (4X8GB) DDR3 12800 1600MHz Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I5 3.2 27-Inch (Late 2013) Me088Ll/A - A6 at Amazon.com
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013