Streamlight CR123A batteries, 3-volt lithium cells with a shelf life of nearly ten years and last about one hour of continuous use. More specifically, the batteries typically have 1.75 hours of maximum brightness run time at regulated maximum intensity. Comes in a pack of 2.
Specifications:

Nominal Voltage	3V
Rated Capacity mAh
Configuration	Stick
Charge Time	N/A
Style	Stick
Includes
ANSI NEDA
Chemical Composition	Lithium Ion (Li-ion)
Size
Rechargeable	No
Quantity	2