How to upgrade RAM iMac late 2013 21.5inch - break & fix MOVIE - YouTube
Apple 21.5" iMac Desktop Computer (Late 2013) B&H Photo Video
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz SODIMM PC3-12800 204-Pin SO-DIMM Max Memory Upgrade at Amazon.com