Desiccant is described by "Unit" rather than size due to the differing absorbent properties of the products used. A "Unit" is the quantity of desiccant which will absorb 3.00 grams of water vapor at 20% relative humidity or 6.00 grams of water vapor at 40% relative humidity. A "Unit" of clay is typically 33 grams.
To determine which Unit size desiccant is best, the following information is needed: 1) type and size of container 2) type and amount of product being protected 3) environmental conditions.