Thanks to its patented memory hinge, Twixit Clever Clips have been shown to open and close more than 1,000,000 times in independent tests - while in extreme temperatures. Twixit's unique bag clips are made of polypropylene plastic, which is approved for contact with food. Secure the freshness of chips, bread, or any food in a plastic or paper bag. Use them to organize around the garage or shop too. Freezer, microwave and dishwasher safe. If Twixit Bag Clips ever loose their shape, simply immerse in boiling water or cycle in the dishwasher. Made in Sweden.