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Backpacker Magazine – September 2011

Gear Review: Mammut Felsturm Half-Zip

Made with Gore-Tex Active Shell this breathable jacket was wearable in a wide range of temperatures.

by: Steve Howe

Mammut Felsturm (Courtesy Photo)
Mammut Felsturm (Courtesy Photo)

The Best Shells. Ever.
See the other three.
>> The membrane Gore-Tex Active Shell. Like the original stuff, it’s expanded polytetrafluoroethylene (PTFE), but this new version is about 50 percent thinner and lighter, plus Gore devised a way to attach the liner fabric using less glue. A non-porous polyurethane (PU) coating protects the membrane from sweat and dirt. The PU also renders the fabric 100-percent windproof (unlike the others in this test, which allow a tiny bit of air to pass through). The hydrophylic (water-attracting) PU draws moisture in, then it’s pushed out through the membrane’s pores by your body’s heat output. The process requires a climate differential between the inside and outside of the shell, which is created by a buildup of humidity and temperature. In simple terms: You work, it breathes.

>>The claim Gore won’t say how much more breathable Active Shell is than previous membranes (nor would it provide a close-up image of the membrane itself), but our testers estimate it to be 20 to 30 percent. A key to that improvement: Gore developed a new lab test using a heated/sweating mannequin, so designers could study “whole body breathability”—not just the breathability of fabric swatches. Gore also works closely with manufacturers to streamline pockets, flaps, and excess lining materials that could hinder breathability.

>> The jacket “Unparalleled temperature range,” says one tester of this minimalist, half-zip pullover. The Felsturm is built with light, supple, fairly open-weave 20-denier nylon and a light tricot liner that result in unsurpassed breathability, negligible weight, and a tiny packed size. “On a ski tour up Utah’s 10,719-foot Lake Peak, it was raining at the trailhead, then sleeting and snowing all day,” says one tester. “Everyone else was constantly swapping layers, but I wore this from start to finish.” Clincher: He didn’t touch the Felsturm’s pit zips all day (though testers appreciated them on warmer trips). The great-fitting hood accommodates helmets, yet cinches well around the cheeks; it sealed out the chill even when ridgetop winds hit 50 mph. Most other features are sacrificed for weight (there’s only one Napoleon pocket). And Mammut sews the smooth-running waterproof zipper coils straight to the shell, trimming the standard strip of tape. The short cut is harness-friendly and loose enough to fit midlayers. 

>> Same technology/costs less Scott USA Crusair Active Shell Jacket ($300, 12.2 oz.,

Price $390 
Weight 10.5 oz. 
Sizes unisex XS-XL

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Reader Rating: -


Mar 19, 2012

amazing ! I bought one,wore it in a mild midwest december rain storm.i walked at a med. fast pace for 2 hours. I went home dry.

Mar 06, 2012

I agree with Sharky, A full zipper provides a very useful way to cool quickly and a half zip just can't compete with that.

Rudy E
Feb 28, 2012

Hey guys, I have purchased over 4 jackets that have gore-tex and claim to be waterproof and breathable. All of my jackets no matter who the maker is, don't really breath as you sweat. I unzip my arm pit zippers, pockets, and main jacket zipper to allow my sweat to escape. In the rain, I only unzip my underarm pit zips. But essentially as one manufacture laughed at me and told me, there are no waterproof jackets that are waterproof and breath. Haha now really!!

Oct 01, 2011

"A non-porous polyurethane (PU) coating". "The process requires a climate differential between the inside and outside of the shell, which is created by a buildup of humidity and temperature".

You state the membrane has a non-porous coating and that a build up of humidity and temperature is created inside the shell, yet you rate it most breathable?

The whole point of "breathable" fabrics is that comfort is improved by reducing the build up of temperature and humidity, not what figures can be produced in a lab test.

Claiming a jacket with a non-porous coating that requires a build up of humidity and temperature to pass water is more breathable than jackets made of fabrics which allow air to pass through is nonsense.

Sep 27, 2011

Maybe the Mammut Felsturm is made of good stuff, but I would never give any jacket a "most breathable" award if it didn't fully unzip. It may be great for sitting in a football stadium, but people who hike or engage in other stenuous activities know what I mean.

Sep 27, 2011

These rain jackets may work fine, but get real! $300 for just the rain jacket? These are not in the price range a lot of folks can afford.

Besides, if you wear them on a hike and you still get wet, either from perspiration or leakage, can you get a full refund?

Sep 27, 2011

Your link to is non-existent...

Sep 27, 2011

Can't tell since no real names were used whether or not this review has any creditiablity. My testers say this is way overpriced by about $380 and and the color is gosh awful. My testers say they'll stick with their current jackets and continue layering which is safer than relying on an individual overpriced rag...


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