SD 109 Renewable Dehumidifier for safes. This is good for an area up to 75 cubic feet. These can also be used in cars, and other spaces where moisture and mildew is an issue. This size is for a 20 gun and smaller safe, also can be used in you car. In an open area, you can renew the dehumidifier by placing it in an electric oven, toaster oven, Air Fryer etc. You cannot renew it in Propane or gas ovens, and these types of ovens have moisture in them.