FRU PN: 40Y8749 40Y8748. Portable 40GB External USB 2.0 Hard Drive. Mistakes do occur. We are happy to be of assistance anytime. Taking into account the 12-hour Time Zone difference we will reply to you within 24 hours.
The twin head USB lead is in case your device does not provide power or enough power on the USB data port, maybe if you are using it with an OTG adaptor (not supplied) for a phone you can plug the other feed into a USB power source to power the drive.