The Mammut Felsturm Half Zip uses Gore Active Shell and has a mix of excellent and poorly designed features that lead us to prefer other lightweight shells. The Felsturm, for example, runs a bit short in the arms and the torso, has pit zips (a feature that we believe is unnecessary on a Gore Active Shell jacket), and lacks a drawcord adjustment at the waist. Other shells we've tested are more comfortable and more durable for the same or less weight. Even so, the Felsturm performs well and score above average in our highly competitive tests.
Check out our complete Hardshell Jacket Review to compare all of the models tested.