Amazon.com: OWC 32GB (2 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S32P) : Everything Else
Apple iMac (27-inch, 2017) review: Apple doesn't mess with success - CNET
Install memory in an iMac - Apple Support
Apple 21.5-inch 4K iMac Teardown Reveals Upgradeable Kaby Lake CPU And RAM | HotHardware
Install memory in an iMac - Apple Support
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
A-Tech 64GB (4x16GB) RAM for Apple iMac 2017 27 inch Retina 5K | DDR4 2400MHz SODIMM PC4-19200 2Rx8 1.2V 260-Pin SO-DIMM Memory Upgrade Kit at Amazon.com
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac
iMac with Retina 5K Display 2014/2015 Memory Upgrades