RAM & Memory Upgrades
OWC 32GB (2x16GB) Compatible with Synology D4ECSO-2666-16G, D4ES01-16G | DDR4 2666MHz PC4-21300 ECC SODIMM 2Rx8 1.2V Memory Upgrade for NAS DiskStation, RackStation, FlashStation, (OWC2C6D42R8032P)
OWC 32GB UPGRADE: Consists of 2pcs of 16GB DDR4 2666MHz PC4-21300 CL19 2RX8 ECC SO-DIMM 1.2V 260-pin Memory Modules Compatible for Synology NAS DiskStation, RackStation, FlashStation, & NVR DVA Servers models: DS1522+, DS1618+, DS1621+, DS1621xs+,...
https://www.bizrate.co.uk/ram_memoryupgrades/owc-32gb-2x16gb-compatible-with-oid33538217895.html