This product is either discontinued or we cannot get that from suppliers.
Synology D4NESO-2400-4G, 4 GB, 1 x 4 GB, Speed PC4-19200 (2400 MHz), DDR4, 260-Pin SO-DIMM, 1.2 V, Non-ECC.
The 4GB DDR4 2400 MHz SO-DIMM Memory Module from Synology. This single RAM module features a capacity of 4GB, a clock speed of 2400 MHz (PC4-19200), and a 260-pin SO-DIMM form factor.