Double-layered SIGG HOT & COLD Glass WMB bottles are made from heat-resistant borosilicate glass. The double layers provide an improved insulation effect. This keeps tea and coffee hot longer and also keeps drinks like fruit and vegetable juices cold longer. The two built-in filters enable anyone to use the bottle according to their individual needs. The long filter is particularly suitable for loose tea, while the short filter is ideal for whole tea leaves or ginger slices. Both filters can easily be removed. The lid is coated in stainless steel 18/8 from the inside, meaning drinks only come into contact with stainless steel and glass. This ensures the taste of the drink is not affected. Pure silicone is used as the sealing material. All materials are of course free from BPA. This bottle keeps your drink 1 hour hot and 2 hours cold.