Zip-Zag leak-proof resealable bags are made of high quality North American food grade plastics. Zip-Zag Bags have taken the term "resealable" to a whole new level. Their patented dual lock zipper seal and quality manufacturing process ensures that all bags are 100% odor free with virtually no oxygen exchange. As an example, the Zip-Zag bags have an oxygen transfer rate of 450 times less than any other zipper locking bag on the market!