The Synology D4EC-2666-16G is a 16GB DDR4 ECC unbuffered UDIMM memory module designed for select Synology NAS units including RackStation and SA series models. Featuring a 2666 MHz clock speed (PC4-21300), 288-pin DIMM form factor, and 1.2V operation, this memory module delivers reliable performance for enterprise storage environments. The ECC (Error-Correcting Code) technology automatically detects and corrects common internal data corruption, ensuring data integrity for mission-critical applications. As an official Synology memory upgrade, this module undergoes rigorous compatibility testing to ensure seamless integration with compatible models including RS4021xs+, RS3621xs+, RS2821RP+, SA3400D, SA3200D, and UC series systems. The unbuffered design provides optimal performance for demanding workloads including virtualization, data management, and 24/7 operations, backed by a 5-year warranty.