Zerust Capsules are ideal for tackle boxes, pistol cases, gun cases, truck boxes, ammo boxes, tool boxes and more. It has proven to be the absolute best way to protect your tackle against rust and corrosion. Molded right into plastic, the patented polymer emits a harmless vapor, forming a protective layer around metal surfaces. All Zerust products will maintain their effectiveness from two to five years or more, so you can count on hassle free, long lasting protection.