This 4 Bay SATA Mobile Rack lets you swap between 3.5in Serial ATA (SATA, SATA II) hard drives in seconds. A time saving storage solution, the mobile rack offers four trayless SATA hard drive bays, allowing you to hot swap Serial ATA hard drives but avoid having to mount the drives to trays for deployment or unfasten them for replacement. Supporting up to four hard drives, each at up to 2 Terabytes (2TB) capacity, the mobile SATA hot swap rack offers a total capacity of 4TB and takes up only three 5.25in drive bays inside a host computer - maximizing space-efficiency within the computer. Using Terabyte hard drives? The HSB430SATBK has two built-in 40mm fans that re-distribute the heat build-up generated as a result of typical drive operation. This feature is especially important for larger volume storage (750GB, 1TB hard drives), and faster "spinning" drives (i.e 7200 RPM), as it can help optimize drive operability and in turn preserve stored data integrity.