Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3L 1600MHz PC3L-12800 CL11 for iMac (Mid 2011, Late 2012, Late 2013, Late 2014 Retina 5K, Mid 2015 Retina 5K) SODIMM Memory Module MAC RAM Upgrade at Amazon.com
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
Install memory in an iMac - Apple Support
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
4GB PC3-12800 RAM for Apple iMac Late 2013 - 27 Inch ME088LL/A Memory Upgrade Module