This 16GB RAM is 100% compatible with the QNAP ES1686dc-2142IT-128G.

Information on memory configuration: The following technical specifications should be considered in advance: RDIMM and RDIMM 3DS (Registered DIMM) or LRDIMM and LRDIMM 3DS (Load Reduced DIMM) RAM can be installed in the device. LRDIMM memory is recommended when large memory capacities are required. RDIMM and RDIMM 3DS memory modules cannot be mixed with LRDIMM and LRDIMM 3DS memory. If a memory upgrade is to be made with the existing RAM, it must be checked which base memory technology (RDIMM / LRDIMM) is present. If memory modules with higher clock rates than specified by the system are offered, the memory clock will automatically adjust to the system specifications.