The stanley 1l classic flask has a double wall stainless steel construction and uses vacuum insulation to keep hot drinks hot and cold drinks cold for up to 24 hours t he stainless steel shell of this flask has a rustproof finish and the entire product is leakproof an easy pour stopper reduces the chance of spillages and makes pouring a refreshing drink effortless this durable flask has a solid lid which doubles up as a cup and a heavy duty handle which makes carrying it over rough terrain ea