Timetec Hynix IC 8GB Compatible for Synology NAS DiskStation DS218+ DS918+ DDR3/ DDR3L 1866Mhz PC3L-14900 1.35V Non-ECC Unbuffered 204 Pin SODIMM Memory RAM (8GB) at Amazon.com
Amazon.com: Synology DiskStation DS918+ NAS Server for Business with Intel Celeron CPU, 8GB Memory, 4TB SSD Storage, DSM Operating System : Electronics
CMS 16GB (2X8GB) DDR3 14900 1866MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Synology® DiskStation DS918+ - A5 at Amazon.com
Parts-Quick 4GB Memory for SYNOLOGY DS918+ DDR3L SO-DIMM RAM Module at Amazon.com
Upgrading Memory on Synology DiskStation DS918+ -
Synology 2019 Configuration Guide Part 3: 16GB RAM specs and how to upgrade your Synology DS918+ – Synoguide
Synology NAS Unofficial Memory Upgrade Guide – NAS Compares