manufacturer says...

Our smallest unit provides lifetime protection for cases containing guns, cameras, telescopes and musical instruments. Also, ideal for tool & tackle boxes and silver drawers - any small storage area. The mini canister contains 40 grams of silica gel in a compact aluminum canister.  Protects 3 cubic feet of enclosed space. [SG-40]

Dimensions:  4" x 2" x ½"

we say...

This 40 gram tin is best for ammo cans and similar smaller volumes.  It may be a good solution for smaller Mono Vaults such as 107 and 207 in short term (perhaps a few months) applications where there is very little room in the MonoVault once packed.  For a couple bucks more, consider the 200g small pack if you can make it fit.  Removed from the carton, the 200g satchel is somewhat maleable for tucking into tight spaces.