A-Tech 256GB (4 x 64GB) Max RAM for Apple iMac Pro (2017) - DDR4 2666MHz PC4-21300 ECC LRDIMM 288-pin Memory Upgrade Kit at Amazon.com
Computers & Electronics :: Refurbished Desktop Computers :: Apple Desktops :: iMac Pro :: 27-inch iMac Pro 2.3GHz 18-core - 256GB RAM - 1TB SSD Intel Xeon W with Retina 5K display
Amazon.com: OWC 256GB (2 x 128GB) PC23400 DDR4 ECC-R 2933MHz LRDIMMs Memory Compatible with Mac Pro 2019 and up Models (OWC29D4LR0256) : Everything Else
Computers & Electronics :: Refurbished Desktop Computers :: Apple Desktops :: iMac Pro :: 27-inch iMac Pro 2.3GHz 18-core - 256GB RAM - 1TB SSD Intel Xeon W with Retina 5K display