Tough, but incredibly thin and light the Microlite 1000 Twist keeps a liter of cold stuff cold for 32 hours, and hot stuff stays hot for 18. That's a long time. Perfect for hydrating on hot days, its advanced engineering goes beyond insulation. The walls are impossibly thin just 2mm so we've shed a bunch of weight and streamlined the profile without sacrificing durable performance. The 18/8 stainless steel is tough and pure, and the secure twist-top is engineered for easy opening even if it's frozen shut and you're wearing gloves.