Ultralight Jacket
Smartwool Men’s PhD Ultra Light Sport Jacket
$115, 4.5 oz. (men’s medium)
Sizes: S-XL
Smartwool Women’s PhD Ultra Light Sport Jacket (hooded)
$120, 5 oz.
Sizes: XS-XL

Whether hiking, trail running, or mountain biking, when I need a jacket to manage variability in my exertion levels and/or the inevitable wind, temperature swings, and maybe light precipitation, I look for a couple of qualities in that shell: high breathability and reeeally low weight. From a chilly and very windy October dayhike of 11,749-foot Mount Timpanogos in Utah’s Wasatch Range, to numerous fall and winter trail runs and rides in the Boise Foothills near my home, in cool temps and conditions all over the meteorological map, Smartwool’s PhD Ultra Light Sport Jacket has had my back. Here’s why its breathability distinguishes this ultralight shell from the competition.

Smartwool Men’s PhD Ultra Light Sport Jacket.
Smartwool Men’s PhD Ultra Light Sport Jacket.

The jacket consists of Smartwool’s thinner-than-a-wafer PhD Ultra Light nylon shell fabric through most of the torso and sleeves, with small vent holes (covered to keep rain out) at the front of the shoulder. With a DWR (durable, water-repellant treatment), the fabric fends off light rain, although it wets through in a steady rain. (It’s not a rain shell.)

But the key to its breathability is a blend of Merino wool and stretchy polyester mesh under the arms and between the shoulder blades, which creates good ventilation without exposing you to much wind or precipitation. When I sweated hard on trail runs and rides in temps in the 40s and 50s, the jacket protected me from cold wind and breathed well enough that it never got more than slightly damp on the inside when my base layer was quite wet. And my base layer would sometimes dry out on long, low-exertion descents, because of the jacket’s breathability.

The regular fit is neither skin-tight nor flappy, and accommodates a couple of light- to midweight base layers. The jacket stuffs easily into its chest pocket to slightly smaller than a liter bottle, but can be squeezed down to about a half-liter when packed; when it’s stuffed, a stretchy fabric loop lets you clip it to a pack or climbing harness.

Hi, I’m Michael Lanza, creator of The Big Outside, which has made several top outdoors blog lists. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Please follow my adventures on Facebook, Twitter, Instagram, and Youtube.


The Smartwool Men’s PhD Ultra Light Sport Jacket on Utah's Mount Timpanogos.
The Smartwool Men’s PhD Ultra Light Sport Jacket on Mount Timpanogos.

The women’s version of the jacket has an elasticized, non-adjustable hood. There’s also a Men’s PhD Ultra Light Sport Hoody ($125, 5 oz.) with an elasticized, non-adjustable hood, a Men’s PhD Ultra Light Sport Vest ($100, 4 oz.), a Women’s PhD Ultra Light Sport Anorak ($130, 8 oz.), and a Women’s PhD Ultra Light Sport Vest ($100, 4.7 oz.).

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The Verdict

For trail runs, hikes, or rides of less than an hour to all day, when you need a light shell for wind and possible light rain and your exertion level may vary, few options are as light and breathable as the Smartwool men’s and women’s PhD Ultra Light Sport Jacket.

BUY IT NOW You can support my work on this blog by clicking any of these links to purchase a Smartwool Men’s PhD Ultra Light Sport Jacket at backcountry.com or the men’s hoodie version at backcountry.com; or a Smartwool Women’s PhD Ultra Light Sport Jacket at backcountry.com or ems.com, or the women’s anorak version at backcountry.com.

Tell me what you think.

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See my review of “The Best Ultralight Hiking and Backpacking Jackets” and all my reviews of ultralight wind shellsultralight rain jacketstrail-running apparelhiking apparel, and outdoor apparel at The Big Outside.

NOTE: I tested gear for Backpacker Magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See categorized menus of all of my gear reviews at The Big Outside.

—Michael Lanza


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