Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
8GB Memory (PC3L-12800, DDR3L 1600MHz) for Apple MacBook Pro 15 inch A1286 Mid 2012. Apple MacBook Pro 13 inch A1278 - Mid 2012. iMac 21.5 inch A1418 Late 2012, A1418 Early 2013,
Install memory in an iMac - Apple Support
Which RAM to buy for iMac 27-inch Late 2012? | MacRumors Forums
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)