Sans Digital MobileSTOR MS4UT+B 4 Bay USB 3.0/eSATA Hardware RAID 5 Tower (Black) Hardware RAID enclosure with hot-swappable slots and dust-free cover. Auto / manual adjustable cooling fan speed to enclosure quiet and efficient cooling. Hardware RAID embedded to the enclosure to eliminate OS compatibility issues. Trayless design and dust-proof front cover. Hot-swap supported. Auto-detected newly inserted hard drive with auto rebuild. Dual Host Interfaces: USB 3.0 (backward compatible with USB 2.0), and eSATA. Easy to read display panel for RAID and system status. Features five different RAID modes, including RAID 0, 1, 1+0, 3 and 5 for redundancy, performance and protections. Also support spanning for simple storage expansion.