Pre-Owned Apple iMac 21.5-inch Desktop "Core i5" 2.9 (Late 2013) 8GB Memory 1TB HDD ME087LL/A - Best Buy
21.5-inch iMac (Late 2013) Review: Iris Pro Driving an Accurate Display
Upgrading the $500 2013 iMac to the Max! - YouTube
CMS 8GB (2X4GB) DDR3 8500 1066MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core 2 Duo 3.06 21.5-Inch (Late 2009) - A35 at Amazon.com
16GB KIT 2X 8GB for Apple iMac 2.7GHz 21.5" Late 2013 2.93GHz 27" Late
Refurbished iMac 21.5" Late 2013 - 2015 - ME086LL/A - CTO | LA Computer Company
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
16GB KIT 2X 8GB for Apple iMac 2.7GHz 21.5" Late 2013 2.93GHz 27" Late
Install memory in an iMac - Apple Support
iMac Upgrade Guide for Intel iMacs
Install memory in an iMac - Apple Support
How to upgrade RAM iMac late 2013 21.5inch - break & fix MOVIE - YouTube
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3L 1600MHz PC3L-12800 CL11 for iMac (Mid 2011, Late 2012, Late 2013, Late 2014 Retina 5K, Mid 2015 Retina 5K) SODIMM Memory Module MAC RAM Upgrade at Amazon.com
Differences Between 2013/2014 iMacs and Late 2015 iMacs: EveryMac.com