The Mountain Equipment Helium 400 is a very versatile and lightweight down sleeping bag. Thanks to its small pack size and low weight, the bag should fit in any rucksack. The sleeping bag is particularly suited for trekking or cycling tours in the summertime. Its thermal efficiency will also be sufficient for cooler nights during the spring and summer months. Thanks to the snug alpine fit, the sleeping bag is extremely thermally efficient and light. Plus, it's so comfortable to sleep in. The 4 baffle anatomically shaped footbox is also very warm and spacious. In addition, the sleeping bag is equipped with an integrated collar with a Lode Lock closure, which is easy to open and close and efficiently retains warmth. The Helium 400 is filled with pure duck down. For the outer shell, Mountain Equipment used very light and compressible Helium 20 fabric. This material is not only tearproof and downproof but also windproof and breathable. The interior is also very light, robust and breathable as well. Plus, it'll feel great on your skin. Of course, the Mountain Equipment Helium 250 down sleeping bag comes with a waterproof stuff sack to keep it dry as well as a cube for storing the bag between tours. With the Mountain Equipment Helium 400 down sleeping bag, your next outdoor adventure will be quite the experience!