Memory module crucial Ballistix bl2k8g26c16s4b DDR4-2X8 GB 2666, SO-DIMM, RET _ - AliExpress Mobile
OWC 16GB (2 x 8GB) PC21300 DDR4 2666MHz SO-DIMMs Memory Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs (OWC2666DDR4S16P) at Amazon.com