The Happy Baby ones are great... the glass is fairly thick and shouldn't break easily... plus they are cheaper than the plastic ones. I only bought glass for my 3rd baby... I wish I'd bought them for my first... would have saved a fortune plus the worry about the plastic chemicals (we heat them).

I don't like the teats that come with the glass ones though... but the NUK ones are compatible if you also have the screw on part.