The S3520BU33ER 2-Bay RAID enclosure offers a high-performance external storage solution, enabling you to build a secure RAID array with two 3.5" SATA hard drives, with the option to connect it to your computer through either an available USB (Universal Serial Bus) 3.0 or e SATA port. For fast data transfers & efficient performance from your SATA III drives, the RAID enclosure supports full SATA III transfer speeds, as well as full USB (Universal Serial Bus) 3.0 transfer speeds. When connected through USB (Universal Serial Bus), the enclosure supports UASP, which offers performance up to 70% faster than conventional USB (Universal Serial Bus) 3.0 when paired with a UASP-enabled host controller. With support for JBOD, Spanning, RAID 0, & RAID 1, the enclosure offers several options that enable you to customize your drive arrangement based on your storage requirements. To maximize both durability & reliability, the external RAID enclosure features high-quality aluminum construction with a built-in fan that helps improve ventilation & maintain a better operating environment for your drives.