Arc'teryx Proton LT is an extremely durable and breathable, synthetically insulated lightweight hoody. It's great for a cold winter days bouldering, or as a key layer when alpine or winter climbing. Keep your eyes peeled on UKC for our review.
Meanwhile a sweaty punter has been wearing the other UKC Proton LT for some snowy hillwalking. Apologies for no hard sends, but come on - balancing along the top of Striding Edge is pretty cool isn't it?
More seriously, an interesting bit of kit - it really isn't very windproof but I suppose that's sort of the point, and once you put a shell over it it's really warm. There was plenty of sweat on the inside of my goretex as I laboured up hill in soft snow with both on but I think that's a good sign, the Proton LT seems to hold no moisture at all.