Steel, Thanks to its efficient vacuum isolation, Miles Thermos Bottle will keep your drinks icy cold for up to 18 hours and steamy hot for up to 6 hours. The isolation also takes care of the condensation and ensures that the liquids don’t end up on the bottom of your bag. The bottle is made of 18/8 stainless steel, therefore your drinks don’t acquire the taste or the smell of the bottle’s previous contents. The material is fully toxin-free and is sturdy enough to survive a life-long use. Switch from the plastic toxic bottles to this ecological option – you will enjoy your drinks in a completely new way and will save the nature too!