Black Diamond Coefficient Jacket
$139, 11 oz. (men’s medium)
Sizes: men’s S-XL
Keeping your body from overheating or getting cold while active is a challenge in shoulder seasons, or anytime you encounter fast-changing weather and temperatures from the 20s to the 50s Fahrenheit. The key is clothing that provides just enough warmth without making you perspire too much, and that moves moisture out quickly when sweating becomes unavoidable. On numerous spring and fall days of hiking and rock climbing in Idaho’s City of Rocks National Reserve and Castle Rocks State Park, and dayhiking in July in Mount Rainier National Park, the Coefficient Jacket hit that ideal balance that kept me from cycling between hot and chilled.
Made with a new Polartec Power Dry High Efficiency fabric that’s exclusive to Black Diamond, the CoEfficient Jacket is surprisingly warm for its weight and low bulk, thanks to a thin, waffle pattern to the fleece, which traps tiny pockets of air that your body heats up. But the fleece is also completely breathable—there’s no wind protection to it—so moisture passes through it readily. Whether climbing, hiking, or belaying, when the warm sun hit me, I could open the full-length front zipper to ventilate without having to pull the jacket off; when the sun disappeared behind clouds, I could zip it up to the high, chamois-lined collar and stay warm. The close fit allows a medium-weight base layer beneath the jacket, while the design and stretch deliver the freedom of movement of a good base layer. And it easily layers under a shell or a puffy jacket.
The Coefficient’s weight and breathability make it incredibly versatile as an outer or middle layer in temps from below freezing to the 50s, depending on your exertion level. That makes this year-round piece a super value for hikers, climbers, backcountry riders and skiers, and snowshoers. Depending on your activity and usual weather conditions, you might also consider BD’s Coefficient Hoody ($159, 12 oz.) or the Coefficient Vest ($119, 8 oz.).
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NOTE: I’ve been testing gear for Backpacker Magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See all of my reviews by clicking on the Gear Reviews category at left or in the main menu.