Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Flimsy

Right out of the box, it was clear that the filter was flimsy. It was bowed in on 2 sides. It certainly looked and felt less substantial than my existing filter. Because of the concavity, I couldn't get it to seat evenly inside the case. If I'd used it, air would have certainly flowed around the concave ends. I put it back in its box and returned it.