Apple iMac Memory - Intel Core i7 3.1GHz Quad-Core 21.5" Late 2013 ME087LL/A CTO - DMS
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
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
Upgrading an iMac — Buchanan Consulting
Refurbished Apple iMac 14,1/i5-4570R/16GB RAM/1TB HDD/21.5-inch/Iris Pro 5200/B (Late - 2013) | Mac4sale