Crucial Bundle with 128GB (4 x 32GB) DDR4 PC4-21300 2666MHz RDIMM (4 x CT32G4RFD4266), Dual Ranked Registered ECC Memory at Amazon.com
32GB 2x16GB DDR4-3200 PC4-25600 2Rx8 RDIMM ECC Registered Memory by NEMIX RAM 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