Apple iMac 21.5" Core i5-4570R 2.70 GHz, 8GB RAM, 1TB HDD, 10.15.6 Lat – PC Retro Shop
A-Tech 8GB Kit (2x4GB) 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
Apple 21.5" iMac Desktop Computer (Late 2013) ME086LL/A B&H
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
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
Memory upgrade: Apple iMac 2012/2013/2014 (Howto)
How to upgrade RAM iMac late 2013 21.5inch - break & fix MOVIE - YouTube