The hardest multi-day mountaineering and alpinism places huge demands on your sleeping bag, it needs to be as light as possible, have the smallest pack size and keep working night after night in exposed conditions. Until now this has required substantial compromises but a revolutionary combination of water-resistant down and PRIMALOFT ® Synergy synthetic fill provides perhaps the ultimate solution.Our Bluesign ™ approved water-resistant duck down resists moisture absorption and dries faster without inhibiting loft to gives ultra-light, super-compressible insulation which, when combined with an entirely synthetic PRIMALOFT ® Synergy underside gives a bag that will keep working even when exposed to damp conditions. Matrix bags are the solution for the harsh realities of the most intimidating future lines.