Apple's new 21.5" iMac with 4K Retina screen has user replaceable RAM and modular CPU
Memory Upgrades for iMac 21.5-Inch 2017
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's New 21.5 Inch iMac Has Upgradeable Parts — That's a Huge Deal
Apple's New 21.5 Inch iMac Has Upgradeable Parts — That's a Huge Deal
Apple 21.5" iMac® Intel Core i5 (2.3GHz) 8GB Memory 1TB Hard Drive Silver MMQA2LL/A - Best Buy
How to Upgrade/Install Memory in a 21.5-inch iMac (Mid 2017) iMac18,1 iMac18,2 - YouTube
2017 21.5-inch 4K iMac memory upgrade kit includes 32GB of RAM, tools to take it apart | AppleInsider
Upgrade your iMac's RAM in less than 5 minutes - YouTube
Holy Mother of Mac, the 2017 21.5″ iMac Is Upgradable | iFixit News
Install memory in an iMac - Apple Support
How to Upgrade/Install Memory in a 21.5-inch iMac (Mid 2017) iMac18,1 iMac18,2 - YouTube
NEMIX RAM 64GB (4X16GB) SODIMM Memory Upgrade Kit DDR4 2400MHz PC4-19200 Compatible with Apple iMac