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. 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. With a low oxygen and moisture transmission rate as well as high light and puncture resistance coupled with the included oxygen absorbing packs, these bags are perfect for keeping your goods completely unaffected by any issues that may occur during long term storage.