Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
Apple iMac "Core i5" 2.7 21.5-Inch (Late 2012), 1 TB HD, 8GB RAM, OS 10.11.6 - Imagine41
NEMIX RAM 16GB Kit (2x8GB Upgrade) DDR3-1600 SODIMM PC3-12800 for Apple MacBook Pro Mid 2012 / iMac Late 2012 / iMac 2013, Late 2014, Mid 2015, Mac Mini Late 2012 at Amazon.com
A First Look At The 2012 21.5-inch iMac, And How It Compares To Generations Past | TechCrunch