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,
2015 A1418 can I upgrade the RAM? - iMac Intel 21.5" Retina 4K Display (2015) - iFixit
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET