Since the American manufacturer, Thermos, came to fame, the term has become slang for vacuum-insulated flasks. Although the terms are largely interchangeable, the original scientific phrasing is 'vacuum flask'. Textured coatings are useful – it’s a nice touch to have a handle on a drinks flask but generally, for a one-litre flask, it’s more useful to have a textured coating that provides grip. We hand-washed each flask with hot soapy water and let them air dry overnight, then ranked them on smell. Button-operated lids are more efficient to use than twist-and-pour stoppers – we found the button-operated lids to be more secure than the twist-and-pour stoppers. Flasks are more 'smell prone' than 'stain prone' – none of the flasks we tested had any staining after cleaning, but some retained a faint coffee smell.

Stay hydrated on the go with our range of travel mugs and flasks. Perfect for keeping your favourite beverages hot or cold, our collection combines style, functionality, and durability. Whether you're commuting to work, heading to the gym, or embarking on an outdoor adventure, our travel mugs and flasks are designed to keep your drinks at the perfect temperature. Choose from a variety of sizes, colours and designs to suit your personal style and needs - we have travel mugs made from bamboo, toughened glass, stainless steel and ceramic. Our insulated travel mugs and flasks are designed to ensure optimal heat retention, so you can enjoy your hot coffee or tea hours after pouring. For those who prefer cold beverages, our flasks are designed to keep your drinks chilled, refreshing you throughout the day. With leak-proof lids and easy-to-use handles, our travel mugs and flasks are designed for convenience and ease of use. Whether you prefer a classic stainless steel design or a sleek and modern look, our range offers something for everyone. We examined each flask and its pouring mechanism and attachments for faults. We penalised flasks that had faults affecting their usability.None of the flasks leaked from the main body – however, some flasks can't be filled to their stated capacity without liquid coming out when you screw on the lid. We dropped each flask five times from 90cm to mimic a dropped flask. Those with large dents that inhibited function or ability were rated low.