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
G.Skill Ripjaws 16GB 2 x 8GB DDR4-2666 PC4-21300 CL19 Dual Channel SO-DIMM Memory Kit F4-2666C19D-16GRS - Micro Center
Mushkin Enhanced Essentials 64GB (2 x 32GB) 260-Pin DDR4 SO-DIMM DDR4 3200 (PC4 | Being Patient
Amazon.com: OWC 32GB (2 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S32P) : Everything Else
CORSAIR Vengeance LPX - DDR4 - 16 GB: 2 x 8 GB - DIMM 288-pin - unbuffered | Dell USA