Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
How to Upgrade iMac Hard Drive or SSD 2012-2022: EveryMac.com
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
Apple iMac Upgrades | SimplyFixIt
Apple iMac compatible RAM and SSD upgrades | Upgradeable