Memory in New $1099 iMac is Soldered and Not Upgradable - MacRumors
How to upgrade the memory of a 27-inch iMac with Retina 5K display (Late 2014 - Mid 2015) iMac15,1 - YouTube
iMac with Retina 5K Display 2014/2015 Memory Upgrades
Upgrade RAM on Apple Retina iMac 5K (Late 2015) / How To install memory - YouTube
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
What to do when your iMac won't turn on?
8GB (2 x 4GB kit) OEM RAM Memory for Apple iMac Retina 5K 27 inch (Late 2014) Core i5 / i7 PC3-12800 DDR3-1600MHz 204-Pin SoDimm
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
32GB Kit (4 x 8GB) PC3-12800 RAM for Apple iMac Late 2014 - 27 Inch Retina
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz SODIMM PC3-12800 204-Pin SO-DIMM Max Memory Upgrade at Amazon.com