When you're hanging on by your fingertips you've every reason to carefully count what you're carrying, right down to the last gram. The Men's Arete Hooded Jacket from Mountain Equipment gives a gossamer layer of insulation and windproofing that's unfazed by rain showers. Using high-quality water resistant 700 Fill Power down feather for insulation and incredibly lightweight Helium 30 fabric for the outer shell, with its funky high sheen. When the sun breaks through and takes the chill out of the air, just tuck your Arete away in its own pocket and clip it on to your harness by its own karabiner carry loop.
Mountain Equipment create a fabulous range of down filled jackets to keep you warm in every situation from a scramble in the Lakes to a first ascent of an unknown giant in Patagonia.