304 stainless steel inner and outer wall, copper thermos technology to prevent heat from entering or leaving the thermos bottle by thermal radiation; Even the top lid is insulated, which means there is no escape for heat when you have a hot beverage and no way for heat to get in if you want to keep it cold! This bottle will hold 17 oz of your favorite beverage, and keep it as hot OR cold as you like. The insulated canteen bottles keep up with your life no matter how tough, how active, or how busy you are; They are leak-proof, rust-proof. reusable, sustainable and environmentally friendly.