These packets are found in a brand new pair of shoes, clothing, and almost anything shipped or bought brand new. On the packet it says "Throw Away Do Not Eat." Well I agree that you should not eat it, but do not throw them away. The Silica Gel is Silicon Dioxide or (SiO2). These little balls of gel are very porous and can absorb as much as 40 percent of its weight in moisture. Or in an enclosed container, it can bring down the humidity to a about 40 percent. You can reuse them when they get saturated by simply re-heating them to about 250-300 Degrees Fahrenheit for about 30 minutes or longer depending on the size of the gel ball. If you want to see how well they work, put a couple packets on your dashboard of your vehicle at night and notice that the fog on the windshield that is usually there in the morning will be gone.
Of course a good coat of oil like Break Free CLP will help, but always keep in mind that moisture will cause rust on metal. There is always moisture in the air as well as in the gun oil itself. Using the Silica Gel packets is an easy, cheap, and effective way at preventing rust in your gun safe.