Third party, used, HDI-30 to DB25 SCSI interface adapter for use on all PowerBook 100 series (except 190) and with all PowerBook Duos via an HDI-30 equipped dock like the Apple Mini Dock. This provides the PowerBook with a standard SCSI port to connect external SCSI peripherals.
In addition, this model supports SCSI Disk Mode (also known as Dock Mode) via a switch, which allows PowerBooks that support this mode to behave like a hard disk and be connected to another Macintosh host.