All of our glass toys are made of 100% borosilicate glass - This type of glass is commonly known for its superior quality which makes it resistant to thermal shock. Borosilicate glass is medical grade, lead free and non toxic which makes it body safe and hypoallergenic. Glass products made of borosilicate glass can stand extreme temperatures making it perfect for temperature play (can be heated or cooled). According to the Mohs hardness Scale, the hardness of glass is borosilicate 3.39.