These elegantly shaped STACKABLE bowls are made from 100% tempered glass and can withstand impact 2.5 times more than normal glassware. The bowls are also freezer safe， microwave safe & dishwasher safe! 

The tempering process is what makes Duralex so tough. Glass that has been heated to around 700°C is suddenly cooled by cold air ventilation. This treatment creates controlled stress in the glass which improves most of its physical qualities: resistance to mechanical stress (bending， impacts) and thermal shock. It is the same tempered glass used to make windscreens which， in the event of an impact or accident the tumbler will shatter into thousands of non-cutting pieces.