These consist of a bright LED and flexible twisted lead wires that have a 2 slot female connector on the end (which can be removed).
You know those blinky lights on the front of your PC tower that shows hard drive activity? These are the same units, consisting of a green LED and 13" flexible twisted lead wires that have a 2 slot female connector on the end. This unit can be dismantled, providing you with some twisted wire, a female to female connector, and a standard 5mm (T1 3/4) green LED. Use it for a tongue and grove battery connector, or a two pin header connector.
Note: This is surplus stock, so get it before it's all gone!