It is safe for change of temperature from -4˚F to 230˚F. Use in the microwave, freezer and dishwasher, kindly open the closure clips while use in microwave. 4-side of locking system makes it possible to be airtight due to equal pressure to all 4 sides. Locks tightly with hollow-center silicone. Food Storage/ Lunch Box/ Kid's Toy/ In the Garage/DIY/Sewing/First Aid.