Crucial 16GB Kit (8GBx2) DDR4 2666 MT/s (PC4-21300) CL19 SR x8 SODIMM 260-Pin for Mac - CT2K8G4S266M System Specific Memory - Newegg.com
Crucial Memory Bundle with 16GB (2 x 8GB) DDR4 2666MHz SODIMM Upgrade kit CT2K8G4SFS8266 Compatible with iMac Retina 5K 27-inch 2019 (iMac19,1) and Mac Mini 2018 (Macmini8,1) at Amazon.com
Apple iMac 27-Inch (2020) Review | PCMag
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How to upgrade the 27-inch 5K iMac (2019) with a massive 128GB of RAM [Video] - 9to5Mac