Instruct: Classify Amazon reviews into positive or negative sentiment
Query: not authentic

The one I received was not authentic so it would not stay on correctly (and I managed to get my full refund). I later bought another one from else where and it stays on and reads sto-fen on it. That said this one that does not stay on correctly, I was still able to use it but have to really work with it to get it correctly positioned. For that this imitation sto-fen gets 2 points. the real sto-fen, I would give a 5 as it definitely does what it is supposed to do and does not give a harsh shadow.