Mammut has scored big with the Butterfly suspension system in its 2005 Ice Pack line. Available in 35 and 45 liter options, the Ice Pack delivers in performance, weight and value. The Ice Packs “winged”, butterfly-shaped frame, made of small tent like poles that actually pivot at each interface, provides superb support, minus the weight. I keep trying to come up with reasons to carry more gear to warrant the use of the 45-liter sample. The simple rucksack design keeps the pack light (1500 grams at 35L), yet it still has everything to carry rope, ice tools, skis, crampons, helmet, whatever. This pack rules when you need to carry it all and want to shave weight as well.