Food grade & 304 stainless steel on both inside and outside walls. Free of BPA materials, chemical toxins or metallic aftertaste transfer. Vacuum insulation creates an airless space between two walls. Virtually eliminating the convection process and temperature change. Double wall insulation maintains hot or cold temperature of contents for a long time. Ideal for carrying a wide variety of beverage. This stainless steel bottle can be used at home, work, at the gym, for sports, in your car, at the beach and even camping or hiking. Typical uses include water, tea, coffee, carbonated drinks, wine & beer.