This 500 ml thermos is made from food grade 18/8 stainless steel that won’t rust and is naturally BPA-free. The high chromium (18%) / nickel (8%) alloy composition makes it highly corrosion resistant and bacteriostatic and is therefore used in the food industry as the gold-standard food-grade stainless steel. Sleek, ergonomic, and durable, it holds the perfect quantity of water, is 100% leakproof, and is easy to carry. Will keep beverages hot for 8 hours (tested) and cold for 24 hours. Best of all, it features its own convenient screw on drinking cup. We all love these at GIAM.