These are made with multi layer film for extra strength. Simply fill with water or your favorite drink. They have standard Nalgene 63 mm loop-top caps which can be easily packed with ice cubes, and accommodate most filters and purifiers. They are collapsible for easy storage in any fanny pack or backpack side pocket. These versatile containers have a gusseted bottom, so they stand upright for easy filling. They are top rack dishwasher safe and withstand temperatures from -20ºF (-29ºC) to 220ºF (104ºC), so you can use for hot as well as cold beverages. Guaranteed leak proof.