Constructed of multi-layer laminated structure such as OPP / AL / NY / PE / PET / AL / NY / PE / OPP / AL / PE and welded with the valve, it provides excellent properties of low OTR and WTR. It is great packing for ground coffee, coffee beans and foods which are sensitive to oxygen. THe carbor oxygen (CO2) can be pulled out through the valve, and prevent outside air to enter in. According to your order.