A-Tech 16GB (2x8GB) RAM for Apple iMac Late 2015 27 inch Retina 5K | DDR3L
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
How to Upgrade/Install Memory in a 21.5-inch iMac (Late 2012– Mid 2014) iMac14,1 iMac14,3 - YouTube