iMac RAM for Model 13.2 to 15.1| DDR3-1600MHz | 4GBx2 | MacMemory.com
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
Memory Upgrades for iMac w/ Retina 5K Display Late 2015
CMS 32GB (4X8GB) DDR3 12800 1600MHz Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I7 3.4 27-Inch (Late 2012) - A6 at Amazon.com
Apple 27" iMac (Late 2012); iMac13,2 Installation Guides and Specifications - Macfixit Australia