The Synology D4ES01 series provides DDR4 ECC SO-DIMM memory modules in 4GB, 8GB, and 16GB capacities. Specifically designed for models like the DS1621+, these 260-pin modules feature ECC technology to proactively detect and repair data corruption, ensuring system stability for business-critical tasks. As official Synology upgrades, they are rigorously tested for seamless DSM integration and are optimized for 24/7 operations, virtualization, and multi-user environments. These modules offer a reliable way to expand system memory while maintaining the high data integrity required for professional storage applications.