Although a very recent (about five minutes ago) convert to the MBB philosophy, I would strongly suggest that people do not skip the vacuum sealing step. Google searching shows me that there are MBB that are vacuum seal ready as well , and I would strongly suggest this over just throwing stuff in a MBB and heat sealing it or whatever. Vacuum > no vacuum, regardless of the permeability of the bag. In regard to the metal foil layer, which was my biggest concern, I was just informed by a very smart friend that the layer of metal on these bags is so thin that it is unlikely to trigger a metal detector. edit: My friend also points out that the metal foil can be an advantage, as packaging in a room with an ionizer present will reduce trace elements of the drug adhering to the outside of the MBB.