64GB (4X16GB) DDR4-2666 PC4-21300 ECC UDIMM Compatible with Synology D4EC- 2666-16G Memory Upgrade Module by NEMIX RAM at Amazon.com
Supermicro 64GB DDR4 MEM-DR464LE-LR26 Server Memory
Apple Memory Module 64GB DDR4 2666MHz SO-DIMMS (2x32GB) - Apple
OWC 64GB (2 x 32GB) PC21300 DDR4 2666MHz SO-DIMMs Memory Compatible with Mac Mini 2018, iMac 2019 and up, Dell, HP, Lenovo, ASUS and Compatible PCs (OWC2666DDR4S64P) at Amazon.com