Apple iMac 21.5" Core i5-4570R 2.70 GHz, 8GB RAM, 1TB HDD, 10.15.6 Lat – Pc Retro Shop
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
Apple iMac 27-inch (late 2013) Reviews, Pricing, Specs
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 at Amazon.com
How to Upgrade Memory in a 27-inch iMac (Late 2012-2013) iMac13,2 and iMac14,2 - YouTube
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
NEMIX RAM 16GB Kit (2x8GB Upgrade) DDR3-1600 SODIMM PC3-12800 for Apple MacBook Pro Mid 2012 / iMac Late 2012 / iMac 2013, Late 2014, Mid 2015, Mac Mini Late 2012 at Amazon.com
Apple iMac review (2013) | Engadget
HOW I UPGRADED MY iMAC 21.5in Late 2013 MODEL (SSD & RAM UPGRADE) - YouTube