referred to as primary packaging. Secondary packaging is that packaging which is outside the primary packaging layer and in the case of general purpose individual operational rations this packaging is used to group several primary packages together. Lastly, tertiary packaging is that used to support bulk storage, shipping, and handling of product in the distribution supply chain. Rations are grouped at this level in fiberboard boxes or cases and subsequently palletized as unit loads for ease and efficiency of handling and distribution. It is preferable that the packaging be easily opened without specific tools. If specific tools are required, they should be included in the ration pack, or alternatively a set should exist containing the ration pack and all necessary specific tools. Primary and/or secondary packaging should be waterproof. Secondary packaging should be insect resistant. Tertiary packaging must be water resistant. It is recommended that the rations be stacked on NATO type pallets (1200 x 1000 millimeters) for standardization purposes. The minimum number of rations on a pallet position (i.e., on one single or on two stacked pallets) shall be 150 days of supply (DOS). The height and weight for a single pallet position, including the pallet(s), shall not exceed 2.2 meters and 1000 kg respectively. A pallet of rations must contain different menus. See also History of military nutrition History of military nutrition in the United States List of military food topics References External links Operational Rations of the Department of Defense, 7th Edition 'Rations information from around the world – MREInfo' Military food