Fabricated Inside And Outside In 18/8 Quality Stainless Steel. Which Is Rust Proof. Use Your Mug For Tea, Coffee, Juice, Etc. Pre-Condition Your Mug With Hot Water, If Using For Hot Beverages And With Cold Water If Using For Cold Beverages. Do Not Use For Carbonated Drinks Cleaning Instructions: * Wash Inside Out With Mild Detergent. Use A Brush For Cleaning The Inside. Do Not Use Strong Detergents, Bleach Or Cleansers Containing Chlorine. * When Not In Use Keep The Flask Lid Open To Avoid Odour.