The Streamlight BATTERY PACK-SURVIVOR/KNCKLHD model 90339 keeps your Survivor or Knucklehead flashlight powered and ready. This rechargeable battery pack ensures long run times and dependable performance in crucial situations. It's a direct replacement, restoring full functionality to your compatible Streamlight flashlight, and providing peace of mind when you need it most. Depend on Streamlight quality for consistent and lasting illumination.