Individual packs are wrapped in clear plastic to give them a two year shelf life. A cube is just 12 individually wrapped Boveda. A brick is a little different, it’s 20 unwrapped Boveda. As long as you re-close the master bag after removing the next round of Boveda for your humidor, they’ll have a two year shelf life inside the bag. Buying by the brick gives you the best Boveda pricing available.