The bottle of this product with thick PVC material, has good impermeability. The screwing lid with environmental polypropylene, is durable, so you do not worry that water will overflow to burn hands when you pour water into the bottle. Moreover, its smooth cover, is comfortable for our skins. Notes: When pouring water into the bottle, you can fill it with two-thirds of its capacity. After filling hot water, please cover the nut, but do not tighten it at first. Then you should squeeze the extra air out of the hot water bottle. At this time, please tighten the nut, but do not over tighten to prevent. After screwing the nut, you should put the bottle upside down, which can make extra water drop and dry it with dry cloth finally. Please note that the pattern of the cover is random.