iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
4GB PC3-12800 RAM for Apple iMac Mid 2015 - 27 Inch Retina 5K MF885LL/A - MF885xx/A Memory Upgrade Module
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
iMac 15,1 (Retina 5K, 27-inch, Late 2014)
How to Install Memory iMac 27-inch 5K (RAM Crucial 16GB) - YouTube
timetec hynix ic 16gb kit(4x4gb) compatible for apple ddr3l 1600mhz pc3l-12800 for imac(mid 2011, late 2012, late 2013, late 2014 retina 5k, mid 2015 retina 5k) sodimm memory upgrade|max slots upgrade - Walmart.com