Hornady Rechargeable Gun Safe Dehumidifier - Absorb humidity and prevent rust or mildew in gun safes or other enclosed areas. Moisture-control crystals change color when unit needs recharging. When recharging is needed, plug into a 110V electrical outlet and dry out the crystals. Quick-Connect Bracket Makes Mounting Unit Easy In Gun Safes, Closets Or Pantries Safeguards Firearms And Other Valuables From Mold And Mildew Contains No Harmful Chemicals And Is Child, Pet And Home Safe Eliminates Humidity In Enclosed Spaces Up To 333 Cubic Feet Removes Humidity Without Electricity Or Batteries