Our take
We score silicone honestly: it’s a synthetic polymer, so purists should reach for glass first. But food-grade platinum-cured silicone is far more thermally stable than the polyethylene film it replaces, and the habit it kills — buy, use once, toss, repeat — is one of the kitchen’s last single-use strongholds. For the freezer and lunch-bag duty glass can’t do, this is the right tool.