Each size contains 50 resealable Mylar bags. These Mylar bags are food grade and rated for long term storage. The 7 mil thickness and Mylar material aid in preventing oxygen and water from penetrating the bag. Because oxygen and water are the two major components that cause food to spoil, packaging in a quality Mylar bag is essential for long term storage. Proper storage can help you maintain quality, ready-to-eat food that is shelf-stable for up to 25 years.