Thermos ThermoCafe Stain Steel Flask 1L Picnic Travel Tea Coffee Drink Hot Cold. This flask features stainless steel vacuum insulation, which virtually eliminates temperature change by creating an airless vacuum space between two stainless steel walls for superior insulation. It has a 1 Litre capacity and a height of 31cm. The flask comes with a twist and pour stopper and is made from lightweight, virtually unbreakable stainless steel construction. It can keep drinks hot for up to 8 hours and cold for up to 24 hours.