Despite the best efforts of science in the quest to stay warm, evolution is still ahead. The down cluster from geese and ducks remains the best insulating material known to mankind. It is more compressible and offers better warmth for its weight than any other fibrous insulation. Down is an incredibly complex structure, made primarily from keratin - an amazing natural polymer that also makes up materials as diverse as wool, horn and hooves. Down has a unique 3D shape optimised to perform as a durable insulating material. From a central core in each down plume grow barbs and from each barb grow barbules, creating a near-perfect structure for blocking radiative heat. Varied and complex cross sections throughout then provide durability and recovery from compression. Despite the natural properties of down, if it is not used correctly, it can be practically useless. If a baffle is too big or filled with too little down then down will move around reducing efficiency and adding weight for no benefit. Conversely, if a baffle is too small or filled with too much down then it cannot loft properly, again reducing thermal efficiency. Laboratory and field testing together with extensive prototyping ensures we get the most from this precious material. Each bag has been optimised for thermal performance, compression resistance, migration control, comfort, and longevity.

A well-fitting sleeping bag is more comfortable and reduces dead air space, maximising thermal efficiency. Our bags are specified to one of four fit blocks; the size and shape of each is developed according to its intended use - whether to minimise weight, sleep in maximum comfort or wear additional clothing. Our patented EXL® system, provides extra warmth and loft by minimising dead airspace - pulling fabric away from the down and encouraging loft. The configuration of baffles is as important as size and shape. Different baffle structures in the main body of our bags are each optimised for the end use. Every factor is taken into consideration: such as the length of time a bag is likely to be used, the environment and conditions. We also consider the effect of componentry and fabrics, and where the balance of cost, weight and bulk need to lie. Our new seven baffled hood, the DC7 LV is a low volume construction. It is more anatomically shaped, lighter, more thermally efficient and easier to adjust than its predecessor. Our range-standard DC5 hood has itself been optimised. Down Control hoods offer a substantial improvement over the lifetime of a sleeping bag. New interlocking zip baffles and collars featuring our Lode-Lock™ closure reduce warm air escaping from the opening. Now, optimised for density, all are filled with the same high quality down as we use in the rest of our sleeping bags offering greater durability than synthetic insulations, better compressibility, and improved thermal performance. Our Trapezium foot pieces optimise down density and reduce seam lines. Using Bulls Eye™ and Sharks Toe™ innovations, their component weight has fallen by around twenty percent.

Fabrics influence both overall performance and the way a bag looks, feels and sounds. They directly affect warmth and loft and are crucial in keeping insulation clean and dry. Water resistant outer fabrics protect the whole bag from the effects of moisture. Fabrics without them can be lighter and more breathable. 2017 sees the introduction of GORE® THERMIUM™. A composite fabric that makes use of both a 10 denier face and a PTFE membrane yet weighs just 38g/m2 is perfect for our Expedition Series of Extreme sleeping bags; our most durable bags for the coldest, most hostile conditions. DRILITE® LOFTTM XERO continues the evolution of our own water resistant fabric programme. Taking the lowest weight achievable for fabric of this type down to as little as 28g/m2. It is purpose made for Super Alpine climbing and the most lightweight high altitude or winter expeditions where protection, pack size and weight are critical. Available in our Alpine Series of Extreme bags it sits alongside our time-tested 55g/m2 DRILITE® LOFTTM II fabric. It delivers a 1500 mm hydrostatic head and is the ideal fabric for sleeping bags destined for serious mountaineering, climbing, and backpacking in difficult conditions. Of our three non water resistant shell fabrics, the new Plasma™ fabric stands apart. Durably lightweight, air permeable and therefore exceptionally breathable, it is one of the lightest downproof fabrics for its strength. Found in our Lightweight Extreme range it is perfect for Alpinists, long-distance backpackers, and mountain athletes for whom minimum weight is the most important factor.

For more than fifty years we have been manufacturing and developing our sleeping bags and through that time witnessed countless Himalayan and Polar expeditions, numerous first ascents and endurance records. Our new range of sleeping bags is born from an exhaustive prototyping and testing programme. Broken down into their constituent parts, every component, every baffle has been considered and re-examined in the pursuit of making it better; lighter and more thermally efficient. More scientific, quantifiable testing than we have ever done before. Building on collaborations that in some cases go back decades. Baffle dimension and density testing at the University of Leeds, cold chamber prototype testing and thermal imaging analysis at the Leeds Beckett University’s Institute of Sport and repeated thermal manikin prototype testing and analysis at the Aitex Institute in Spain. Cold chamber testing in particular has played a major role in informing our developments. By providing a controlled environment in conjunction with thermal imaging data we can gain insight into not just the hard details such as whether any part of the bag is less thermally efficient but also offer the softer details in terms of how we interact with a bag. How easy is it to adjust the collar? How closely does the foot piece feel when the temperature is well below freezing? By combining scientific observations with feedback from real people we understand how a design fits and functions in demanding conditions. The final part of our prototype and testing programme are mountain trials on some of the most challenging Alpine winter routes and expeditions to the Himalaya.