Although the USB flash drive duplicators are intended for use with USB flash drives, they can be used with external hard drives.
Note: Due to the slower copy speed of the USB flash drive enclosures, using an external hard drive as the source of the copy can take a considerable amount of time. USBDUP12 and USBDUP15 both copy at 1.5 GB per minute. Therefore, if you use a 1 TB external hard drive as the source of a copy, it would take roughly 11 hours to complete.