Timetec 8GB Compatible for Apple Late 2015 iMac (27-inch w/Retina 5K Display) DDR3L 1867MHz / 1866MHz PC3L-14900 2Rx8 CL13 1.35V 204 Pin SODIMM Memory Module MAC RAM Upgrade for iMac 17,1 at Amazon.com
Timetec 8GB Compatible for Apple Late 2015 iMac (27-inch w/Retina 5K Display) DDR3L 1867MHz / 1866MHz PC3L-14900 2Rx8 CL13 1.35V 204 Pin SODIMM Memory Module MAC RAM Upgrade for iMac 17,1 at Amazon.com
4GB PC3-12800 RAM for Apple iMac Mid 2015 - 27 Inch Retina 5K MF885LL/A - MF885xx/A Memory Upgrade Module
How to upgrade the memory of a 27-inch iMac with Retina 5K display (Late 2014 - Mid 2015) iMac15,1 - YouTube
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
iMac with Retina 5K Display 2014/2015 Memory Upgrades
Mac Ram Experts | Australia's Best Apple Ram Upgrade
iMac with Retina 5K Display 2014/2015 Memory Upgrades
32.0GB OWC Memory Upgrade for 2012-2015 iMac
A-Tech 16GB (2x8GB) RAM for Apple iMac Late 2015 27 inch Retina 5K | DDR3L 1866MHz / 1867MHz PC3L-14900 1.35V 204-Pin SODIMM Memory Upgrade Kit at Amazon.com