The Mammut Felsturm Half Zip is the third lightest hardshell we tested. It features Gore Active Shell and mixes some excellent features with some undesirable features.
The Felsturm's zipper is the best anorak zipper we tested because the zipper flows smoothly, has a large zipper pull that's easy to grab with gloves on, and angles left of your chin. It's significantly better than the Mountain Hardwear Quasar's zipper. The hood is reasonably good; it covers your chin more than most lightweight shells, adjusts well for having two drawcords (most hardshells have three), but we found that it can be restricting when worn over a helmet. Of our other top rated lightweight shells the Mountain Hardwear Quasar has a better hood for wearing underneath a helmet and the Arc'teryx Alpha FL's hood is better for wearing over a helmet.
The Mammut Felsturm's hood covers your chin very well.
The Felsturm has an excellent elasticized mesh backed external chest pocket that's easy to open and stores a surprising amount of stuff. We prefer this pocket to both the Alpha FL's and Quasar's chest pockets. And the jacket's stuff sack is by far the best that's included with any hardshell tested. It's the perfect size and has a reliable hang loop on the back that can be used to attach the shell to a harness. Several of our testers chose to use this shell for committing alpine rock routes specifically because of its stuff sack. For comparison purposes, the Quasar does not include a stuff sack and the Alpha FL's sack could be smaller and lacks a reliable hang loop.
The Mammut Felsturm also doesn't have an adjustable wrist, which can let in cold air. Other jackets do a much better job here. See the Mountain Hardwear Quasar.
This author believes that the Felsturm's pit zippers are unnecessary on a jacket with Gore Active Shell. Their added ventilation can be beneficial in certain circumstances, but the majority of a jacket's venting happens with the front zipper. The Arc'teryx Alpha FL uses the same materials and has an equally trim if not trimmer fit, yet we felt no need to vent the jacket more than half a zipper's length. Similarly, the Mountain Hardwear Quasar has a half-zip and no pit zips, and performs very well. The Felsturm would be lighter, and therefore better, if it didn't have pit zips.
Like all lightweight shells we tested, the Felsturm has a trim athletic fit. Unfortunately, we found the jacket's arms and body to be a bit on the short side; the sleeves left exposed skin at the wrists, and the bottom hem often rode up from underneath our harness. Furthermore, the jacket skips a drawcord adjustment at the wasist (it uses a lightweight elastic). As a result, wind and cold air enters the jacket. A simple and lightweight elastic drawcord would be better — the 9.5 oz. Mountain Hardwear Quasar and 4oz. Patagonia Houdini both have them. If you only use the Felsturm for it's ideal application (alpine climbing), however, your harness will seal the waist well.
The Felsturm's hit or miss features, and the fact that the shell weighs 20 percent more than the lightest tested, is why the Arc'teryx Alpha FL and Mountain Hardwear Quasar scored higher. As for value, the Felsturm costs $50-$75 more than those top two rated lightweight shells.
The Mammut Felsturm doesn't have an adjustable waist. Cold air comes in unless you're wearing a harness.