No Damp Dehumidifier is the effortless way to help control the excessive humidity that leads to musty odors, stains or corrosion aboard stored boats, RVs or seasonal homes. The special crystals automatically remove moisture from the air, depositing it safely in the convenient container. Great for cabins, heads, closets and other enclosed spaces. The Ultra Dome's large size makes it perfect for protecting large boats, RVs and other larger enclosed areas.