Mini Butterball Replacement 8.4V 6600mAh lithium ion Rechargeable Battery Pack for LED XM-L T6 Bicycle Light, headlamp, Head Light and Flashlight Replacement battery pack for LED XM-L T6 bicycle light, headlamp, Head Light and Flashlight. Made of 6 x high performace 18650 batteries. It is ideal for device that require large capacity but very small discharge current. Extends the life of the bicycle light or headlight. Easy to carry and use, would make your travel life more convenient.