The inside makes all the difference

A vacuum flask keeps drinks warm thanks to the insulating double walls of the inner vessel. These can be made of glass, metal or plastic. We only use glass and metal for our products, because plastic is not as effective at retaining heat. A glass inner vessel is best if you will be using the flask at home. But if you plan to take the flask on excursions, you should choose one with a metal inner vessel. It's tougher and can take the bumpy ride in your backpack or picnic basket.