They are NOT borosilicate glass! Many years ago, they were. But they haven't been for at least 20 years now. They WILL sometimes explode on you if you use them directly over a gas flame, and you'll get showered with boiling water, glass, and (in my case ~10 years ago) sulfuric acid. DONT DO THAT! Buy some REAL borosilicate lab glassware or other cookware that specifically tells you that it's OK to use on the stovetop. All of the current "Pyrex" cookware does tell you not to do this, but usually only on the box it came in, and in small print. Useless.
I'm not much for government intrusion in commerce, but this seems to be one case where that brand name, which now has an impossible-to-get-rid-of association with certain technical properties (like not exploding due to thermal shock) should not be allowed to be used on glassware that cannot be used safely over a flame.
Be careful out there.