They hold water, that's how they do it. Very difficult to turn - there is a pink ring that you have to pull to "turn". The plastic was so warped around the edges that I had to separate the pieces by hand. Once I opened it up, the plastic should be flexible enough to fold but strong enough to hold water securely and not break. Pulp Filled with water, I take it by the handle, it stretches and doesn't feel strong at all when carrying it. When it's on the ground, it stands up a bit and looks like it's melting or leaking. As said, it retains water, which is why it gets three stars. Will definitely not buy again.
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