https://www.qnap.com/en/product/qm2-m.2ssd

Quad M.2 2280 PCIe NVMe SSD expansion card
Connector: 4 x M.2 2280 PCIe (Gen3 x 4) NVMe SSD slots
PCIe and Lanes: PCIe Gen3 x 8
Bracket: Low-profile (default). Low-profile flat and Full-height brackets are also included.
Dimensions (L x W x H): 204.95 x 68.9 x 20.6 mm; 8.07 x 2.71 x 0.81 inch

https://www.qnap.com/en/compatibility/index.php?device_category=expansion%20card&brand=qnap

Note: The TS-x77 and TVS-x82(T) series only supports installing the QM2 in the System Zone PCIe slot (PCIe slot 1).
Please check the M.2 SSD compatibility list and QM2 Installation Guide