Synology 2-Bay Expansion Unit for Increasing Capacity Network Attached Storage DX213 Internal HDD: 2x 3.5" or 2.5" SATA2 (hard drives not included) Expansion Port: 1 Volume Type: Synology Hybrid RAID, Basic, JBOD, RAID 0, RAID 1 Noise Level: 19.9 dB(A) Fan: 92 x 92 mm Power Recovery: Sync with the connected DiskStation (Default Mode) Maximum Operating Altitude: 10,000 feet