Thanks to The Stanley QuadVac construction that minimises heat loss via convection, conduction and heat radiation due to its four layers and a wall thickness of 1 mm plus the use of 18/8 stainless steel, the Master Series vacuum insulated bottles stand out by being extraordinarily robust and for being able to retain heat for up to 40 hours. These features, in combination with a vacuum-insulated closing lid with stainless steel coating and a pour-through stopper, which goes far into the bottle, result in a high quality insulated bottle. The Master Series products are also leak proof, BPA free and dishwasher safe.