First of all, we must look at the appearance of the cup: see if the surface of the liner and the outer shell are evenly polished, whether there are bruises or scratches.
Second, see if the mouth welding is smooth and consistent, which is related to whether the feeling of drinking water is comfortable;
Third, look at the quality of plastic parts. Not only will it affect the service life, but also affect the sanitation of drinking water;
Fourth, see if the internal seal is tight. Whether the screw plug and the cup fit properly. Whether it is free to screw in and out, whether it is leaking. Fill the glass with water for 4 or 5 minutes or use a few taps to verify that it is leaking. Look at the insulation performance, which is the main technical indicator of the vacuum cup. Generally, it is impossible to check according to the standard when purchasing, but it can be filled with hot water and then feel the hand. If the cup that is not insulated is filled with hot water for two minutes, the lower part of the cup will heat up, and the lower part of the insulated cup is always cool.
