TEAMGROUP Elite DDR4 16GB Single 2666MHz PC4-21300 CL19 SODIMM 260-Pin Laptop Memory Module Ram - TED416G2666C19-S01 at Amazon.com
V-Color 32GB (2 x 16GB) ECC SO-DIMM DDR4 2666MHz (PC4-21300) for NAS Micro Server/Workstation/Compatible with Synology 21 Series 2Rx8 CL19 1.2V (TES416G26D819K-VKC) at Amazon.com
16GB (1x16GB) DDR4-2666MHz PC4-21300 1.2V SODIMM Laptop Memory by NEMIX RAM at Amazon.com
A-Tech 16GB RAM Replacement for Synology D4ECSO-2666-16G & D4ES01-16G | DDR4 2666 MHz PC4-21300 SODIMM ECC Unbuffered Memory Compatible for NAS & NVR Servers at Amazon.com
V-Color 64GB (2 x 32GB) ECC SO-DIMM DDR4 2666MHz (PC4-21300) for microservers, workstations, Networking Platforms and Embedded Systems 2Rx8 CL19 1.2V (TES432G26D819K-VC) at Amazon.com
Crucial 16GB Single DDR4 2666 MT/s (PC4-21300) DR X8 SODIMM 260-Pin Memory - CT16G4SFD8266 at Amazon.com