I have no criticism of the processing, cleaning or optics. But did not mind that for people like me who love hot tea, because they always feel cold, a feel-good factor is eliminated when the cup is cool outside. OK, it's probably a sense of things that you do not burn your hands, but you will burn more easily the mouth. I simply just looking for a cup of that long hot holding the tea (what it does even halfway satisfactory). Am now but again switched to Standardhäferl and thermos from which I nachschenke, when the tea cools.