Review on 20 oz Cupture Double Wall Insulated Plastic Mason Jar Tumbler Mug with Striped Straws - 3 Pack by William Mahajan

They're really good! Polycarbonate plastic is durable and crystal clear. Never wash them in the dishwasher. They've printed that warning below, but it's easy to miss. Typically, polycarbonate plastics are very sensitive to temperature changes, so hand wash them in warm water. In fact, they are not isolated. At least not much. There is no seal above. In fact, where the straw goes by, there's a gaping hole. There's a reason a thermos has a thick, sealed lid: the insulation works best when it's all over the place. So don't expect them to keep your cold drinks cold or your hot drinks hot much longer than a regular glass. We didn't care. They are pretty graceful.