The Thermos Mountain FFX 500 ml is a stainless steel vacuum flask built for mountain conditions, where having a hot or cold drink on hand for hours matters more than shaving grams. Double-wall vacuum insulation holds heat for 24 hours and cold for 24 hours, enough to cover a full day out or an overnight hut stay without needing to reheat anything.
At 500 ml it sits in the middle of the range — 280 g is noticeably more than a simple water bottle, but reasonable for a double-wall vacuum design. The narrow-mouth opening makes pouring precise, and the screw cap with a seal keeps it leak-proof even tipped over inside a pack; the steel is BPA-free and rated for hot liquids like tea or soup.
Available in black or red, it is hand-wash only — not dishwasher safe. A silicone base and a removable protective ring shield the steel from knocks and drops on rock, which suits trips where a base of gear is carried in a pack rather than ultralight setups where 280 g would be a noticeable line item.