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 (up to 6 Gbps), as well as full USB (Universal Serial Bus) 3.0 transfer speeds (up to 5 Gbps). 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 (see our performance below). 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. The HDD enclosure offers a versatile solution for increasing the storage/backup capabilities of your computer, with support for large capacity hard drives (tested up to 4TB), & is backed by a Star Tech.com 2-year warranty & free lifetime technical support.