This B&H Kit includes Synology DX1211 12-Bay Expansion Unit and 12 x 4TB Hitachi Deskstar 3.5" SATA III Internal Desktop Hard Disk Drives, providing you necessary storage and fast access to a large amount of data. The Expansion Unit delivers an effortless solution for volume expansion and data backup for Synology DiskStation DS2411+ / DS3612xs NAS.The DX1211 Expansion Unit provides an easy way to scale up the storage capacity of Synology DiskStation DS2411+ / DS3612xs NAS by adding 12 hard drives. The RAID volume on DS2411+ / DS3612xs server can be expanded directly without having to reformat the existing hard drives. In addition, the unit securely connects to the DS2411+ / DS3612xs NAS via an Infiniband cable to carry 12 Gb/s SATA signal for maximum throughput. It allows the hard drives in the connected DX1211 unit to operate as internal hard drives of the DS2411+ / DS3612xs with no lag in data retrieval. The Hitachi Deskstar Desktop Hard Disk Drive is a stellar upgrade for your desktop computer's hard disk drive. It holds a huge capacity of 4TB and fits into your computer's 3.5" drive bay. The drive features a SATA III interface that can deliver enhanced data transfer speeds. This hard disk drive uses a ramp load/unload design that eliminates direct contact between the read/write heads and the disk platter, minimizing the risk of shock damage. The design also improves the drive's reliability and power efficiency.