The North Face recently asked me if I wanted to review a pre-release pair of their new Verto S4K GTX boots. Without hesitation I said yes because everything I had read about the Verto S4K GTX's sounded fantastic. The boots did not disappoint. My one sentence review of these boots is that I will never be a good enough climber to use them to their full potential. These boots were designed to climb, and they were designed well. The first thing I noticed about the S4K's was the aggressiveness of them. These boots were made for alpine climbing. They are most definitely not a general mountaineering boot that was tweaked to improve climbing performance. The S4K's were designed from the ground up as a mixed terrain boot. When I laced them up for their first adventure I was taken aback by the fit of the boots because they didn't feel like any boot that I had ever tried on. I was truly surprised by how securely my heel locked in place. Every boot I have owned in the past has resulted in gnarly blisters from that little bit of friction from my heel rubbing with every step. My heel in the Verto S4K's was locked and going nowhere. The North Face calls this healCradle, I call it awesome. The other thing that stood out on the Verto S4K's was the toe box. This boot was made for climbing and as a result the toe box is more akin to a climbing shoe than it is to a traditional mountaineering boot. I took a picture comparing the toe box of the Verto S4K to the toe box of La Sportiva's Trango Alp. As you can see the S4K's is much more form fitting. My foot fits fine in both boots while wearing a liner with a beefy wool sock, but with the S4K's there isn't a lot of wiggle room. Personally I liked it. I have average width feet so if you have wider than average feet you might be SOL. Also if you're prone to getting cold feet then I'd be aware that these might reduce circulation and be problematic for you. So far I have only done a few snow slogs and a bit of ice climbing in these boots. The snow slogs were in the heavy, wet PNW snow and my feet stayed completely dry. It wasn't particularly cold so I cannot attest to the warmth of these boots but I would imagine that they'd be able to handle almost everything but the burliest weather in the lower 48. Ice climbing with these bad boys was straight up phenomenal. I have a pair of Grivel G-12's and the heel welt on the S4K's was more than sufficient to hold my crampon securely in place. What made these boots phenomenal while ice climbing was the slight down turn in the toe. It was not obvious while I was hiking but when I was front pointing on some moderate water ice I definitely noticed a little something. The actual sole of the boot is not turned down like a climbing shoe but rather the insole is. It is the little things like this that really wow'ed me. Also while I was front pointing my heel was still solidly in place. For a half-shank boot the S4K's are impressive. My foot was secure in the boot, which was locked to the crampon, which was glued to the ice. It was a really wicked combination that brought a smile to my face. These boots are not perfect though. In my limited testing of them the one thing that was less than ideal was the pressure in the toe box while I was traversing long, moderate snow slopes. While I was traversing the outside of my down hill foot would get a bit achy. I think this was a combination of the tight toe box and the fact that they were brand new. As I continue to break them in I am pretty sure it will go away but only time will tell. This is a review in progress of the Verto S4K GTX boot. As I get to know them better I'll post more. I have yet to take them scrambling or rock climbing but I am sure they'll perform superbly. All things considered this boot is fantastic. It fits my foot well, it is thoughtfully designed, and it is built to climb harder than I will ever be able to.