The CMS STACK 3 External SCSI Hard Drive ST-138N is a vintage unit specifically designed for Apple Macintosh computers with a SCSI cable. This product allows users to expand the storage capacity of their vintage Macintosh systems, making it ideal for those looking to store or access large amounts of data from a classic computer setup. The CMS brand ensures quality and compatibility with older Macintosh models, providing a reliable solution for vintage computing enthusiasts.