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 (27-inch, Late 2012) - Technical Specifications
How to Upgrade/Replace the Memory in a 21.5-inch iMac (2019) iMac19,2 - YouTube
Install memory in an iMac - Apple Support
Teardown of New 4K 21.5-inch iMac Reveals Removable RAM and Modular CPU - MacRumors
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
iMac (21.5-inch, Late 2012) - Technical Specifications
64GB RAM upgrade kit for 21.5-inch iMAC now offered by OWC - 9to5Mac
A-Tech 8GB RAM for Apple MacBook Pro (Mid 2012), iMac (Late 2012, Early/Late 2013, Late 2014, Mid 2015), Mac Mini (Late 2012) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
iMac | 2.7 GHz Intel i5 | 21.5 Inch | Late 2012 - Techable.com