The Apple HDMI to DVI Adapter allows you to connect your Mac with built-in HDMI to a DVI display or projector. You can use an external display as your primary display, extend your desktop to a second display, or work in mirroring mode with a projector so you can view what your audience sees.
Use the HDMI to DVI Adapter to connect a single-link DVI digital monitor, such as the 20-inch or 23-inch Apple Cinema Display, that includes a DVI connector. Review the documentation or check with the manufacturer of your monitor to make sure you're choosing the right adapter.