Moisture barrier bags are specialty bags engineered with multiple laminated layers, including a layer of aluminum which provides a barrier against moisture vapour and atmospheric gases, to maintain a dry environment.
Additional layers can be added to the outside of the bag to increase the strength of the bag to prevent puncture. Different layers can also be incorporated to assist with providing a static shield, UV protection and more.

This style of bags has many applications including shipping small circuit boards, medical supplies and devices, as well as chemicals and adhesives. Larger format bags are commonly used to protect high value items when shipping via sea container, often this is achieved by placing a sheet underneath the product you are packing, loading the component onto that sheet, and then dropping a cover over the top part, the base sheet and upper bag components can then be sealed protecting the component side. 
These bags can be fitted with humidity indicators to indicate the condition of the air inside the bag, they can also have valves to allow for the air inside the bag to be vacummed out, along with built in desiccant packs.

These bags are certified to ISO standards and are often a requirement in Mil-Spec's ASTM, and ISTA pckaging guidelines including:
MIL-PRF-131L Class 1
MIL-PRF-81705 Class 1 (ESD/Anti-static variant)
MIL-STD-2073 (MIL-SPEC Packaging method)
MIL-DTL-117

At SmartShield we recommend you work with a member of our team to ensure the moisture barrier bags are well suited to your application.