Double-glazed windows of this type are made of tempered glass.
The tempered glass strengthens it by 4-5 times and significantly reduces the risk of possible harm to human health from broken glass. When broken, tempered glass turns into small fragments that can not cause serious harm to humans. Due to this quality, they are considered to be safe double glazing windows. 

It has the following advantages:
•    toughness (it is hard to break glass)
•    safety (when breaking glass it turns into small pieces)
translucency