This Apple Mini DisplayPort to DVI Display Adapter is designed to allow users of a Mac computer featuring the Mini DisplayPort connector to output to an external monitor or projector that features a Dual-Link DVI port. In addition, it also features a USB extension cable that runs alongside the DVI cable, for convenience sake. Both video-mirroring and dual-display modes are supported.
Please check with the manufacturer of your monitor to make sure you're choosing the right adapter.
Mini DisplayPort to Dual-Link Display Adapter, with USB Extension