Operating during colder seasons requires more kit, whether you like it or not. Accompanying frost on your flysheet is a heavier pack, thicker clothes and probably a larger sleeping system too. We need this extra kit to stay warm and comfortable when the temperature drops. There are a few accessories that punch above their weight and supply warm moments when out on the hill that can increase your comfort. Read our full review of the Sigg Thermo Flask, both 1 litre and 0.3 litre.
Sigg Thermo Flasks are made of stainless steel and are vacuum insulated. Keeping liquids hot for up to 24 hours and cold for 30 hours (1 litre version) and 9 hours hot, 12 hours cold for the 0.3 litre version. The drinking parts are easily dissembled for cleaning and the seals can be fully removed.
The 0.3 litre version comes with a great tea filter which fits neatly inside, whereas the 1 litre has a mug attachment.
I have been using both flasks for over two years almost every day and they have held up extremely well. My real world observations for the 1 litre are about 9 hours for hot beverages, sometimes in conditions down to -20ºC. The 0.3 litre version keeps drinks warm for about 6 hours.