On cold summits and shoulder-season hikes, we appreciated the Houdini Air’s extra touch of heat. The jacket’s double-weave material combines 90 percent nylon and 10 percent polyester so that the poly forms a slight waffle pattern on the inside, which traps warm air (and also keeps the fabric from sticking to skin). The design served us well during moderate hikes in the Tetons with temps in the 30s, but we got hot during steep pushes. The Houdini Air blocks wind up to 25 mph and shook off light rain for about 20 minutes. One chest pocket fits a smartphone.