The SEC-1 is a cost-effective, rack mount expansion chassis, supporting 4 removable or fixed 3.5" SCSI disk, tape, or cartridge drives. The SEC-1 supports all current 3.5" SCSI disk systems. SEC-1 chassis can be daisy-chained to support additional drives. The SEC-1 is a modular system and is available with numerous configurations to suit most applications.
 

Image shows Rack Mount SEC with Removable Disk Drives.