LiFePO4 9.9V 2100mAh TRANSMITTER PACK, for any transmitter using Standard 2x2x2 BLOCK 8-Cell (9.6V) Nimh packs. Includes Safety PCM circuits to allow charging inside Transmitter, using standard wall NiMH charger. These are LiFePO4 Transmitter Power Packs, with high-rate 3.5mm gold charge/discharge plugs, and Hyperion-style Balance Tap.