First, the lid of the newly bought thermos cup can't be closed because the lid doesn't match the mouth of the cup, and it can be replaced for free after the warranty period.

Second, the reason: the quality of the new thermos cup must meet the following two conditions to prove that the quality is no problem.

1, it feels difficult to twist: the new thermos cup feels difficult to twist because the sealing rings are all new, and it feels difficult to twist because there are cracks and no wear.

2. Seeing a crack, it is because the elasticity is uneven. From another perspective, on the contrary, this is a truly brand-new product that has not been moved. Because the seal is tight enough and elastic enough, it will not leak.

Third, matters needing attention:

1. With the increase of use times, the sealing ring will wear faster (this is a consumable), so it needs to be replaced once a year.

3. When the lid is infinitely close to the cup body, it means that the seal has been seriously worn and needs to be replaced with a new thermos cup before drinking.