The Men's Nimbus Insulated Jacket looks like a down puffy, but Rab stuffed it with Cirrus synthetic. Powered by 3M Featherless, Cirrus insulation dries quickly, stays warm when wet, and provides a surprising amount of warmth despite its light and lofty feel. Rab protects this innovative insulation with a Pertex Quantum shell, featuring an optimum strength to weight ratio, extreme abrasion resistance, and windproof comfort. The lining is air permeable, which means that the jacket starts to breathe the moment you put it on, unlike standard breathable jackets that start to breathe once you sweat. There's an internal pocket for security, and one of the hand pockets doubles as a stuff sack for compact convenience that clips to harnesses and backpacks.