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
HOW TO UPGRADE NEW 2017 IMAC RAM - YouTube
Amazon.com: Mid 2017 Apple iMac with 3.0GHz Quad Core i5 (21.5 inch Retina 4K, 16GB RAM 256GB SSD) (Renewed) : Electronics
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac
Install memory in an iMac - Apple Support
Memory Upgrades for 2017 iMac 27-Inch
Apple iMac Pro 27-inch (2017) 3.0GHz 10-Core Intel Xeon W-2150B 64GB RAM 2TB SSD AMD Radeon Pro Vega 64