They're made of reinforced Pyrex type glass. As long as you don't throw it at a wall or give it any kind of serious trauma (dropping it on the concrete from a second story window, running over it with your car) it should be fine. This glass is usally
...
They're made of reinforced Pyrex type glass. As long as you don't throw it at a wall or give it any kind of serious trauma (dropping it on the concrete from a second story window, running over it with your car) it should be fine. This glass is usally shatterproof, so if it does break, it will only break into a couple of pieces.
If you have questions about materials, please tread the Materials Page. You can find this as a link on the product page. Here is the one for Pyrex Glass.