This product is either discontinued or we cannot get that from suppliers.
Qnap RAM-4GDR3LA0-SO-1866, 4 GB, DDR3L SDRAM, Speed 1866 MHz, Number of Pins 204-pin, Form Factor SoDIMM.
The 4GB 204-Pin 1866 MHz SO-DIMM DDR3L RAM Module from QNAP is designed to run at 1866 MHz frequency. The 204-pin module is compatible with the TS-x53B series.