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Arc'teryx Rho AR Review

The Arc'teryx Rho AR is a great first or second layer in cold and frigid temperatures, as long as you avoid sweating while wearing it
Arc'teryx Rho AR
Arc'teryx Rho AR Zip Neck
Credit: Arc'teryx
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Price:  $145 List | Check Price at REI
Pros:  Warm, excellent fit, soft inner layer, layers well
Cons:  Low breathability, limited to use in low activity, slow drying speed
Manufacturer:   Arc'teryx
By Ross Robinson ⋅ Senior Review Editor  ⋅  Dec 19, 2016
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Our Verdict

We had high expectations for the Arc'teryx Rho AR, partially because of past experiences with this manufacturer, and partially because it's astronomical price tag must equate to incredible performance (or at least, that's what we thought). In several categories, such as comfort, warmth, layering ability, and durability, this top hit its target. Our reviewers truly appreciated the soft inner fleece, insulating and flexible fabric, and bomber seams. However, its relative breathability and drying speed weren't up to par with the rest of the products in this review. With these two significant drawbacks, we found it tough to justify the price, especially considering the availability of other competent models.

Our Analysis and Test Results

The Rho AR by Arc'teryx is a synthetic, midweight long underwear top that can also double as a mid-layer. It is very warm and has a cozy and soft interior. It also features an excellent fit without restricting mobility. However, it didn't breathe as well as the other models in this review and had a slow drying speed after becoming saturated. There are several things we like about this model, but its $145 price tag isn't one of them.

Performance Comparison

Arc'teryx Rho AR long underwear - ross robinson in the rho ar from arc'teryx, heading up the iconic el...
Ross Robinson in the Rho AR from Arc'teryx, heading up the iconic El Misti shield volcano in Arequipa, Peru. The below-freezing temperatures required a warm top like this one, but we were somewhat disappointed in its breathability when we began to sweat.
Credit: Ross Robinson


The Rho AR looks warm, and it certainly is. It scored the highest of all models in this category. It is also one of the heavier products we reviewed, coming in at 10 oz. With a very snug but comfortable fit, it traps heat very well. The sleeves and torso are extra long to allow for a full range of movement without exposing wrists and belly-buttons to the air. We would have appreciated a strip of material behind the zipper to block air from coming through this extra porous zone though.

Arc'teryx Rho AR long underwear - when you need a warm top for daybreak summit pushes, the rho ar is...
When you need a warm top for daybreak summit pushes, the Rho AR is ready for the wake-up call.
Credit: Ross Robinson

Arc'teryx Rho AR long underwear - from top to bottom: the microchill 2.0, the warm, and the rho ar. we...
From top to bottom: the Microchill 2.0, the Warm, and the Rho AR. We generally favored the versatility provided by zip-neck tops.
Credit: Ross Robinson
When things get too hot, the 9 ½ inch zipper can quickly release excess heat. However, even with this feature, we found it easy to overheat when engaging in moderate activity. When hiking El Misti volcano in southern Peru, we worked up a sweat in this base layer underneath a down jacket before the sun came up at 18,000 feet above sea level, despite temperatures below freezing. When worn as a first layer, this top performs best in no to low activity, even in cold conditions.


By comparison, this Arc'teryx model is one of the least breathable tops we reviewed. Being so warm, it was easy to work up a sweat in this product. Instead of immediately wicking this moisture away, it often condensed on the inner jersey fabric, where it stayed until it could be transmitted to the external environment. When this happened high up on the side of a volcano, the cold, condensed sweat chilled us whenever we stopped for a break. Although it didn't take very long for this moisture to move away from our body, it was 2-3 minutes longer than we wanted in cold conditions.

While it didn't score very high in this metric, its score is relative the other very breathable products in our selection. The Rho AR does provide breathability superior to most hard and softshells, rain jackets, and wind shirts.

Comfort and Fit

The Rho AR is one of the most comfortable base layers. The soft jersey inner fabric felt great against our skin. Its super stretchy material fits snugly along the contours of our torsos, providing one of the best fits of all. This top also stayed in place very well, so that we weren't constantly adjusting it. The flatlock seams maintain a low profile and are placed away from areas typically high in chafing. With substantial side and underarm gussets, this product has great mobility as well.

Arc'teryx Rho AR long underwear - the arc'teryx model was the only one to feature a pocket, which was...
The Arc'teryx model was the only one to feature a pocket, which was useful for small items like a key or some cash for a post-summit celebratory beverage.
Credit: Ross Robinson

Drying Speed

Coming in at the back of the pack in our drying speed test, the Arc'teryx model didn't overwhelm with speedy dry times. However, there was a silver lining. Like the merino wool products, the synthetic fabric of the Rho AR was difficult to saturate with water, as it resisted soaking up the water. The top upper ¾ of this model dried out quickly, as all the water drained to the bottom ¼, where it took a very long time to evaporate. If we had been in the backcountry when this happened, we would simply wring out the bottom quarter of the shirt to speed up the drying process. But, to keep the test standard and fair, we didn't.

If you find yourself soaking wet away from shelter in this Arc'teryx product, we recommend wringing out the lower portion of the shirt, as the water will gravitate toward this spot more than in other base layers.

Layering Ability

The Rho AR stood out as the best above the rest in layering ability. We were able to put this top over and under anything that we would consider using as a layering system in the outdoors. Over t-shirts and even thicker base layers and under jackets and mid-layers, this long underwear product performed like a champ. Considering its low breathability, our main reviewer tended to wear this model primarily as a mid-layer.

Arc'teryx Rho AR long underwear - when skiing in the sierras, we liked the comfy, warm, and flexible...
When skiing in the Sierras, we liked the comfy, warm, and flexible combination of the SmartWool as a base layer and Arc'teryx model serving as a mid-layer, with a hardshell overtop.
Credit: Ross Robinson


This Arc'teryx model is one of the most durable tops featured in this review. Its fabric is strong, and the triple and quadruple-stitched seams appear ready to endure a heavy beating. The fabric isn't snag-proof, though, which showed in a few spots after three months of heavy use. Most annoyingly, this product could be confused for a pharmaceutical company with the amount of pilling going on all over its surface. This occurred after just a few uses and stayed around ever since.

Arc'teryx Rho AR long underwear - the pilling of this model turned a once great-looking top into...
The pilling of this model turned a once great-looking top into somewhat of an eye-sore.
Credit: Ross Robinson

Using a razor, you can remove the unaesthetic pilling from this shirt. However, for a shirt that costs $145, we wish this wasn't necessary.

Best Applications

The Rho AR is best used as a first layer in cold and frigid weather during periods of limited physical activity. We prefer not to break into a sweat when in cold conditions with this model. It also serves as an excellent second layer over performance t-shirts and other base layers.

Arc'teryx Rho AR long underwear - the rho ar is built for the cold, but its inability to breathe very...
The Rho AR is built for the cold, but its inability to breathe very well made it only appropriate to lower-level activity.
Credit: Ross Robinson


This contender is very pricey, costing $145. While it performed very strongly in multiple categories, we found it hard to justify spending so much on a product that didn't provide all-around performance, nor truly specialize in any use.


The Arc'teryx Rho AR had the potential for winning a Top Pick award. It's very warm, ultra-comfy, and durable. We were also impressed with its versatility, easily doubling as a mid-layer when necessary. However, its low score in breathability took it out of the running, as this is a very important characteristic for quality base layers. We still enjoyed wearing this model, but found its extreme price tag just as severe of a drawback as its below-average breathability and drying speed.

Ross Robinson
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