The Synology D4ES01 series offers DDR4 ECC SO-DIMM memory modules in 4GB, 8GB, and 16GB capacities, specifically designed for the DiskStation DS1621+ NAS system. These unbuffered ECC memory modules feature a 260-pin SO-DIMM form factor, providing reliable error-correcting code functionality to detect and correct data corruption in real-time. As official Synology memory upgrades, these modules undergo rigorous compatibility testing to ensure seamless integration with DiskStation Manager (DSM) and optimal performance in demanding workloads including virtualization, multi-user environments, and 24/7 operations. The ECC unbuffered design delivers enhanced data integrity and system stability for business-critical applications, backed by a 5-year manufacturer warranty.