The technical blurb that comes with it and that is on the Columbia website states it is constructed of Omni-Tech® waterproof-breathable 3-layer fabric, so it stops wet weather short while allowing excess heat and interior moisture to escape. Full seam sealing reinforces stitching lines, and waterproof zippers keep both you and your pockets dry. Clean, classic mountaineering lines combine with 2-way stretch mobility for the kind of adaptability that the true mountain enthusiast demands.
The jacket has 4 external pockets, two hand warmer pockets which are lined with mess on the inner side and a sort of fleece on the other, plus two chest pockets. These pocket zips are waterproofed, and there is also under arm zips for ventilation.
Now to say I put this jacket to the test would be an understatement, a week of skiing followed by some serious winter hiking in the Mont Blanc region. When putting it to the skiing test I found this jacket to be excellent, it has plenty of stretch to allow free movement and kept me warm at all of the right times while having ventilation to stop me from getting too warm. The only draw back of the jacket in the snow sport environment would be the lack of a snow skirt, which to be honest for me is not a major issue. However as I fell in some of the deep powder it was one of those brief moments, as the cold snow found it's way up my back, when I did think it would have been a nice addition.
As excellent as the Deep Ghyll was in the snow, nothing could have prepared me for how adaptable it was when I was doing some winter hiking the following week. The weather for the entire week seemed to throw everything at me, from glorious sunshine, to gale force winds and torrential downpours. I'll be honest when the sun was out it was a little too warm for the jacket so I did take it off, but it's not designed to be a summer jacket. Although when the weather turned this was when the jacket really proved it's worth. It kept me dry and warm during the heavy rains, it also kept me warm during the gale force winds, and although it doesn't profess to being windproof, I certainly would class it as more windproof than some of the actual windproof jackets I've owned in the past. Another plus for the jacket is that it is indeed very breathable, I'm a sweaty person when it comes to exercise and if I don't have the right kit on, I tend to soak myself. So given the exertion I put myself through, I fully expected there to be some moisture build up either on the inside of the jacket or at worse on my base layer, however this jacket was very breathable and let my sweaty moisture escape keeping me cool and dry, even in a downpour.
As good as the jacket proved to be I did find a few picky faults with it, as I mentioned before a nice addition to the jacket would be a snow skirt for those who wish to use this shell on the snow. Another draw back with this jacket is the length of time it took to wear in, it could have just been the jacket that I bought but I did find the zips underneath my armpits to be rather stiff when I first wore it, which did dig in to me. However after a few wears they seemed to mould around me, and I forgot all about them. The jacket can be a rather snug fit as well, not room for too many layers underneath the jacket. I think if you are larger than the average gent, you might find the jacket to be quite tight across the chest, I'm not the biggest bloke and while it was fine for me I could see if I was any bigger it probably would cause a slight issue, although the stretch in the jacket would probably counterbalance this.
In conclusion I found this to be a very good jacket, a few small issues with it but nothing that would put me off buying it again. It's a very good value jacket, especially in comparison to some of the other jackets I looked at purchasing. All in all a big thumbs up from me.