This sale is for a rare Apple Macintosh PowerBook Target Disk Mode SCSI Adapter Cable. This adapter cable requires connection to the standard HDI-30 port on many PowerBook 100 series portables, the PowerBook Duo series with MiniDock adapter, PowerBook 190c, PowerBook 500 Series. Part number is 590-0718-A. This is a dark gray adapter that has a 50-pin connector that may be used with a supported SCSI 50-pin to 25-pin connector cable to be used with another Macintosh desktop or laptop to access the targeted PowerBook's internal hard disk drive that are SCSI based (IDE drives are unsupported). The adapter is approximately 6 inches. Please check the configurations of your Apple devices prior to purchase to verify compatibility, no returns please.