Protect your valuables against rust and corrosion. When the moisture control crystals turn pink, recharge unit by placing it in the oven. Unlimited recharges ensure a lifetime of use. Protect firearms and other valuables from rust and corrosion. Desiccant crystals change color when canister needs recharging. Recharge canister by placing in a 300degF oven until drying granules turn blue (up to 4 hours). Unlimited recharges, no batteries required.