USB Rechargeable Ni-MH AA,1450mAh Batteries (2 included in the pack).

These 1450mAh AA size batteries simply plug into any powered USB port to be recharged.  They're a brilliant idea for  battery operated PC input devices such as a mouse or keyboard. They have an incorporated LED charge status indicator, and they can also be recharged by any 250mA Ni-MH charger.