What is special with the TrailBreak is its slightly tapered shape that makes the flask easier to slide into your backpack and also safer to grip. Just like Primus' other vacuum bottles, Trail Break is a double walled flask with vacuum insulation. Made of high quality stainless steel the flask is extremely durable and great for all sorts of adventures even in rough environments, which makes TrailBreak ideal for mountaineering or hiking. The stainless steel has no treatment on the inside and therefore will not affect the taste of the content. The cup is also made from double walled stainless steel to keep the beverage hot or cold. The large opening makes it easy to fill and clean. Would you want to drink directly from the flask just replace the regular stopper with the supplied ClickClose stopper.