A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz SODIMM PC3-12800 204-Pin SO-DIMM Max Memory Upgrade at Amazon.com
Don't Upgrade The RAM In Your New Apple iMac, Do This Instead
Can you upgrade the RAM in the 27-inch iMac? | iMore
Apple 21.5" iMac Intel Core i5 2.3GHz 8GB RAM 256GB SSD MHK03LL/A Mid 2017 Model | eBay
How to Upgrade iMac RAM (20" and 24" Aluminum): EveryMac.com
Apple iMac review (21.5-inch, 2015): 4K is optional, faster hard drives shouldn't be | Engadget