Battery compartment for holding a single R17670 lithium-ion rechargeable (4.2V) battery. Provides a typical 2.5 hours of runtime on the High setting. The R17670 battery compartment is 33mm (1.3") longer than the CR123 battery compartment. The raised button extends past the end of the switch cap to allow easy operation under all conditions, including use with gloves. The switch cap unscrews and is easily exchanged. The switch is gold plated and sealed against contaminants. DO NOT use 2 CR123 batteries in this battery compartment - it will damage your flashlight.