iMac (21.5-inch, Late 2012) - Technical Specifications
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
A-Tech 8GB RAM for Apple MacBook Pro (Mid 2012), iMac (Late 2012, Early/Late 2013, Late 2014, Mid 2015), Mac Mini (Late 2012) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
iMac 21.5-inch Late 2012 – Full Tech Specs, Release Date, and Price
Apple iMac (Late 2012) review (21.5- and 27-inch) | Macworld