Adamanta 64GB (2x32GB) Memory Upgrade for 2020 Apple iMac 27" w/Retina 5K Display, 2019 Apple iMac 27" w/Retina 5K Display, 2018 Apple Mac Mini DDR4 2666Mhz PC4-21300 SODIMM 2Rx8 CL19 1.2v DRAM
DDR4 | 2019/2020 iMac | SO-DIMM | iMac Memory
OWC 16GB PC21300 DDR4 2666MHz SO-DIMM Memory Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs (OWC2666DDR4S16G) at Amazon.com
2019 5K iMac RAM Upgrade Guide - YouTube
Memory Upgrades for 2019-2020 iMac 27-Inch - Up to 128GB