This product is either discontinued or we cannot get that from suppliers.
QNAP TS-473-4G 4 Bay Diskless NAS, AMD R-Series RX-421ND quad-core 2.1 GHz , Turbo Core up to 3.4 GHz, 4 GB DDR4 (2x 2 GB), 4x SATA 6 Gbps (3.5/2.5-inch SATA hard disk drives, 2.5-inch SATA solid state drives), 2 x M.2 2260/2280 SATA 6Gb/s, 2x PCIe 3.0 x4 Slots, 4x GbE RJ45.
The TS-473 is powered by a high-performance and energy-efficient AMD R-Series CPU and provides two PCIe slots for greater functionality. You can install a QNAP QM2 expansion card to add M.2 SSD caching/10GbE connectivity.