U320 or SATA hot swap module.Support RAID storage application. Large storage capacity in compact space (fit 5x HDDs in 3x consecutive 5.25 bays). Time saving setup (use DIP switches for setup, SCSI terminator on board, and auto-detection for LVD/HVD/SE). Superb environmental detection (SAF-TE function is added on U320 version). Pass rotation / vibration certification to maintain optimal HDDs performance. Unique design with 2 hot-swap fan modules. Excellent thermal solution (15,000 rpm HDD thermal ready) .