Apple iMac A1418 21.5 Inch Late 2012 Intel Core I7 3.1 GHz 8GB Ram 1TB Catalina - Juicy Lucy's Steakhouse
Install memory in an iMac - Apple Support
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
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