I bought the glass markers for normal water glasses from IKEA. These are stackable and thus somewhat thick-walled. Unfortunately not keep the little birds on them. For wine glasses but they are also very useful, since they have been cut too wide. I think that they just stick to such glasses, which have exactly the right thickness of glass - not very practical. And then you still hope that the glass is top wide enough for you, it pushes down while drinking every time ...
