RS1221RP+ compatible RAM
SODIMM
D4ES01-4G 4GB
DDR4 ECC Unbuffered SODIMM
EAN: 4711174724031
D4ES01-8G 8GB
DDR4 ECC Unbuffered SODIMM
EAN: 4711174724055
ECC
D4ECSO-2666-16G 16GB Buy in UK USA
DDR4 ECC Unbuffered SODIMM
EAN: 4711174723676
ALTERNATIVES:
Timetec DDR4-2666 16GB Replacement for Synology D4ECSO-2666-16G DDR4 ECC
ECC Unbuffered SODIMM 2666MHz PC4-21300 260 Pin 1.2V CL19 Dual Rank 2Rx8 Memory RAM Upgrade
Buy in USA