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Under Armour ColdGear Reactor Run Funnel - Women's Review

a breathable, comfortable winter layer with an excellent collar
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under armour coldgear reactor run funnel for women running shirt review
Credit: Backcountry
Price:  $90 List
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Manufacturer:   Under Armour
By Lauren DeLaunay ⋅ Senior Review Editor  ⋅  Feb 14, 2019
  • Comfort - 30% 8.0
  • Breathability - 30% 6.0
  • Drying Time - 20% 6.0
  • Features & Versatility - 20% 8.0

Our Verdict

Living in California, we get pretty used to sunshine and a warm breezeā€¦ until the winter comes. And that's when we realized our current running shirt review just wasn't going to cut it! This winter, we added two long-sleeve options for those of us who just can't stop running when the temperatures drop. The Under Armour ColdGear Reactor Run Funnel, aka the "Reactor," is an impressive layer, combining breathability with comfort and a load of awesome features. It is a bit pricey, to tell you the truth, but we just couldn't compete with this shirt's winter compatibility. The Reactor wins our Top Pick for Winter Workouts, so let us tell you why!
Great features
Boxy fit

Our Analysis and Test Results

Performance Comparison

under armour coldgear reactor run funnel for women running shirt review - what's better than a winter run in bishop, california?
What's better than a winter run in Bishop, California?
Credit: Lauren DeLaunay


Comfort can mean different things to different people, but the Reactor received unanimous praise from our testers. The soft materials, stretchy fit, and comfy collar won it a high score, but its boxy fit and short torso docked it a couple points.

The Reactor's polyester/elastane blend was much cozier than the vast majority of its short-sleeve competitors. If you don't need something mega warm, but you do need long sleeves to protect your appendages on winter days, the Reactor might be the perfect layer for you.

This shirt is super stretchy, much more so than our summer layers. The Reactor does have flatlock seams, something our testers truly obsess over, and we always appreciate when a shirt's seams are removed off the top of the shoulder to prevent chafing or rubbing when wearing a pack.

under armour coldgear reactor run funnel for women running shirt review - you don't have to worry about wind sneaking in the reactor!
You don't have to worry about wind sneaking in the Reactor!
Credit: Lauren DeLaunay

The shoulders and upper torso have an athletic fit, but the bottom was a bit strange. This shirt flares out around the waist, which we found less than flattering. Additionally, it was short, and when we stretch our arms upward, our stomachs become exposed and a cold breeze slipped on.


To be fair, when we decided to add two winter layers to this review, we didn't expect either of them to be as breathable as their lighter counterparts. That being said, we were pretty impressed with the Reactor's ability to keep us dry and warm at the same time, something that's hard to come by with any base layer!

The Reactor has some great paneling, our term for describing a manufacturer's decision to methodically apply different materials to different parts of the body. Reaching from the underarm down the side, this garment has a lighter material to help heat escape. Our testers agreed that the Reactor is very breathable, so if you're looking to crank up the volume on a cool day, this might be the better choice.

under armour coldgear reactor run funnel for women running shirt review - is your workout heating up? not with the reactor's genius underarm...
Is your workout heating up? Not with the Reactor's genius underarm paneling!
Credit: Lauren DeLaunay

Drying Speed

During our months of hands-on testing, we realized that shirts really have two things going on that are working simultaneously to keep us cool, dry, and comfortable: breathability and drying time. Breathability, as we described above, measures how well a shirt lets heat and moisture escape. Drying time, on the other hand, tells us how quickly a shirt wicks away moisture once it has been saturated.

The Reactor was both breathable and a fast dryer, thanks mostly to its lighter material and lack of fleece. Its polyester fabric dried impressively quickly. This is absolutely key to keeping us from freezing during a winter workout. When a shirt gets wet and takes too long to dry out, that moisture makes us cold the moment we stop moving or when a breeze catches up to us. If your winter workouts involve high-octane activity, there's no denying why the Reactor is our Top Pick for Winter.

under armour coldgear reactor run funnel for women running shirt review - take a close-up look of the reactor's interior (below) and exterior...
Take a close-up look of the Reactor's interior (below) and exterior (above).
Credit: Lauren DeLaunay

Features & Versatility

We've already reviewed women's base layers on the site; in this category, we wanted to find the products that were truly meant for running. To do this, we asked runners near and far what features are included in their favorite garments. Our team, then, awarded extra points for shirts with reflective logos, sun protection, odor control, and, in the case of our long-sleeve products, excellent thumb loops.

The Reactor is an excellent shirt for running, thanks to its reflective (albeit small) logos on the back and front. The thumb holes on this shirt were low-profile, but not as comfortable as we could've asked for. That being said, we're very glad that any thumb loops were included.

under armour coldgear reactor run funnel for women running shirt review - showing off the reactor's lighter internal collar and its heavier...
Showing off the Reactor's lighter internal collar and its heavier layer with drawstring.
Credit: Lauren DeLaunay

One of the winter-specific features that this shirt has is a funnel neck. Not quite as tight as a turtleneck, we adore the way the Reactor keeps us warm without constricting our movement. This shirt's funnel is actually twofold: on the inside, there is a light, mega-breathable layer that can be pulled up over the face and nose. This layer is unbelievably stretchy. Surrounding this layer is a heavier one, made of the same fabric that is featured on the torso. The piece has a drawstring closure which is a true rock-star at keeping wind from slipping down our shirt. The combo of these two layers is truly innovative.

Best Applications

Despite being on a mission to find the best winter running shirt, we're happily walking away with one of our favorite pieces for any winter activity. The funnel neck is a great compliment to skiing or traveling in windy places. The breathable material makes this shirt just as great for running as it is for hiking, cross-country skiing, or climbing. Let's be real: you can take the Reactor just about anywhere.

under armour coldgear reactor run funnel for women running shirt review - while we're thankful for this shirt's thumb loops, the design wasn't...
While we're thankful for this shirt's thumb loops, the design wasn't our favorite.
Credit: Lauren DeLaunay


We knew there would be a downside. Despite an incredible performance, the Reactor is one of the most expensive running shirts we've tested. However, if you really need a technical winter layer to wick moisture and keep you warm and sweat-free, this shirt just can't be beaten.


After miles and miles of running, hiking, and skiing, we knew one thing: the ColdGear Reactor from Under Armour is a top-notch piece of outdoor equipment. If you're in the market for one do-it-all winter layer, look no further than our Top Pick award winner. With excellent comfort, superb breathability, and an expertly designed neck, the Reactor is worth every penny.

under armour coldgear reactor run funnel for women running shirt review - thanks to the reactor's reflective striping, we can keep running...
Thanks to the Reactor's reflective striping, we can keep running long after the sun sets.
Credit: Lauren DeLaunay

Lauren DeLaunay

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