Instruct: Classify Amazon reviews into positive or negative sentiment
Query: poor design and cheap materials

I received one of these travel mugs in the mail and when I first removed the plunger from the mug I discovered that it was impossible to put the plunger back in because the plastic parts around the base of the plunger were being pushed out by the metal coil inside (probably meant to make the plastic more durable but actually accomplishing the opposite). I sent the mug back and received a second mug. This one had the same problem. The metal ring doubles over on itself and where it does, it pushes the plastic tabs on the plunger out. This makes it difficult (or impossible) to fit the plunger back inside the mug. I can only imagine how easily these will snap off if one is not extremely careful about fitting the plunger in the mug. I'm returning this one as well and would advise against purchasing this item unless the company changes their design.