The Fisher Labs 26650 Lithium-Ion Rechargeable Battery is designed for use with the Receiver from the TW9000 Multi-Frequency Underground Utility Locator and Line Tracer System Kits. This lithium-ion style battery provides more than double the operating time of two D-cell alkaline batteries. At full charge, the 26650 is capable of providing the receiver with more than 17 hours of operation. Use of this li-ion battery requires the ADAPTOR26650 Battery Holder and Adapter (not included) to fit the battery into the receiver.