New 21.5-inch iMac least repairable yet due to lack of RAM, hard drive upgradability - 9to5Mac
HOW I UPGRADED MY iMAC 21.5in Late 2013 MODEL (SSD & RAM UPGRADE) - YouTube
iMac 21.5-inch (Mid-2014) – Tekhouz Solutions LLC
Apple iMac compatible RAM and SSD upgrades | Upgradeable
2012 21.5-Inch Apple iMac Review: Slim, Sleek, And Stylish, But Far From Shallow | TechCrunch
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Adamanta 16GB (2x8GB) Apple Memory Upgrade DDR3L 1600MHz SODIMM Compatible for iMac (Mid 2011, Late 2012, Early/Late 2013, Late 2014, Mid 2015), MacBook Pro (Early/Late 2011, Mid 2012), Mac Mini RAM at Amazon.com