NEMIX RAM 64GB (4X16GB) SODIMM Memory Upgrade Kit DDR4 2400MHz PC4-19200 Compatible with Apple iMac
iMac 21.5-inch 4K (2017) Review | Trusted Reviews
Install memory in an iMac - Apple Support
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac
Teardown of New 4K 21.5-inch iMac Reveals Removable RAM and Modular CPU - MacRumors
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