Tiny LED light (Warm White), Battery holder with switch, and one CR2032 battery.
The battery should last for over 100 three to four hour games. I had one of these lights on my desk for testing purposes that had been on for 449 hours and was still going, although it was starting to get a bit dim.
Battery is replaceable when if finally runs out of energy.
Avaialble assembled and ready to use or in kit form where you do the soldering.