The 750 gram silica gel unit protects 57 cubic feet of enclosed space. The 4"x 6" steel canister has a built-in indicator that turns from blue to pink to signal when to reactivate. Unit reactivates easily in any conventional oven. This heavy duty unit is preferred by police armories, hospitals, museums, as well as individual collectors. Provides lifetime protection for lockers, cabinets, vaults, safes, and more.