This product is either discontinued or we cannot get that from suppliers.
Synology RAMEC2133DDR4-8G, 8GB, FF DIMM 288-pin, PC4-17000, Speed 2133 MHz, Dual rank, 1.2 V, DDR4 SDRAM, System specific.
RAM capacity can be expanded on selected Synology NAS servers for boosted performance and responsiveness under high system loads. To ensure the optimum durability and compatibility.