NightWriter Battery Refill Kit - Fits The Pilot's Pen, NightWriter LED Pen. AG4 battery pack This battery pack fits the Pilot's Pen "NightWriter", unique LED Powered Pen Includes two (2) complete battery pack refills - including housing. Easy to replace by unscrewing the pen top removing the old battery pack and replacing with the new pack Economical replacement battery pack extend the usefullness of your Pen Two complete replacement packs per order