Synology D4NESO-2666-4G, RAM DDR4, Capacity 4 GB, Unbuffered DIMM (non-ECC), Clock speed 2666 MHz. The 4GB DDR4 2666 MHz Non-ECC SO-DIMM Memory Module from Synology. This single RAM module features a capacity of 4GB, a clock speed of 2666 MHz (PC4-21300), and a SO-DIMM form factor.