These Dry-Packs 5 Gallon Mylar Bags with Moisture & Static Shielding and 2000cc Oxygen Absorbers are made from multiple layers of Mylar and aluminum, making them both durable and secure for whatever items you might be shipping or storing. The flexible structure makes it easy to heat seal with hot iron, effectively blocking out moisture or any other damaging factors. Best of all, these bags are resealable after opening, allowing for repeated use, and the oxygen absorbers keep your goods free of contamination.. Whether you're storing metal or electronic equipment, pharmaceuticals, or food for long periods of time, these bags are perfect for keeping items in an airtight environment.