Pyrex glass is the most popular brand name for borosilicate glass. It is a common material used in glass sex toys such as dildos and butt plugs. Pyrex glass is very strong. It is resistant to cracking or breaking. Pyrex glass heats up and cools down quickly making it great for (careful) temperature play.
The main constituents in borosilicate glass are boron trioxide and silica. Items made from borosilicate glass are less susceptible to thermal shock than other glass items due to its low coefficients of thermal expansion.