REI Co-op Midweight Base Layer Crew - Women's Review

The REI Co-Op Midweight features a polyester and spandex blended fabric that never limits range of motion, thanks to the four-way stretch design. Our testers love the discreet thumb loops and longer cut that increase overall warmth and make the top easier to layer. The thoughtfully placed flatlock seams increase comfort when shouldering a heavy pack and also inspire confidence that this base layer will last for many adventures to come. While not the highest performer in terms of breathability, our testers would recommend this base layer for moderately cold weather pursuits when you are not generating a ton of sweat that needs to be wicked away from the body and released through the tightly woven fabric.

Performance Comparison

Warmth

While not the warmest nor the thickest base layer that we tested, the REI Co-Op Midweight features a tightly woven synthetic fabric that will help protect you against the cold. This layer features quite a slim fit and a 92% polyester and 8% spandex fabric construction that successfully trapped body heat during our cold weather activities. Our testers love the thumb loop feature that covered the majority of our hands when fully extended and kept our digits warm when the temperatures dropped. We also love the longer fit that increased warmth below the waist to our hips.

During our fall trail runs, we noticed that while the layer was able to trap our body heat and move sweat away from our skin, the fabric held onto the moisture generated after gaining some elevation. We found that this lowered the level of warmth the layer can maintain when dry, and therefore, we only recommend this layer during moderate activities. While the midweight fabric itself provides enough warmth for shoulder seasons when the temperatures aren't consistently below freezing, the thin layer will not be warm enough as a stand-alone piece during those winter days on the chairlift.

Breathability

When compared to other synthetic base layers in this review, the REI Co-Op Midweight does not offer a competitive performance in terms of breathability. The slim fit and tightly woven fabric seem to prevent the layer from breathing, as well as other layers that are more air permeable, allowing more moisture to be wicked away from the skin.

On a long trail run, our testers noticed that the layer successfully wicked moisture away from the body, but did not successfully evaporate the sweat out the layer. This issue was compounded when we layered the top beneath other fleece and synthetic jackets as the base of the system trapped moisture and thereby reduced the overall warmth. That being said, it performed well during moderate activities such as hiking or rock climbing in the shade when you aren't necessarily working up a sweat during high-output activities such as backcountry skiing or trail running.

Comfort and Fit

The REI Co-Op Midweight features soft and stretchy fabric and a slim fit. The long cut extends beyond the torso, which not only increases warmth but also allows the layer to remain tucked in, a feature our lead tester appreciated when wearing with her harness during fall days at the crag. While we would agree that the fit is true to size, it is slim, hugging your curves and fitting tightly around your shoulders. If you're after a loose-fitting base layer, this would not be our first recommendation.

The polyester and spandex-blend fabric feels soft next to our skin, softer than you might expect from a synthetic layer. We appreciated the 4-way stretch design that never limited our range of motion and the flatlock seams strategically placed to prevent chafing when wearing a backpack. All in all, our testers were satisfied with this slim-fitting base layer thanks to its stretchy fabric built to move with you throughout a variety of activities.

Durability

After an extensive three-month testing period during the fall in Yosemite Valley and Indian Creek, we subjected this layer to every abrasive activity we could think of, from long trail runs to the rims to off-width climbs up to 150 feet in length. We're happy to report that we experienced no issues with durability after multiple adventures and washes.

Perhaps our only complaint in this metric is that the synthetic fabric smells almost immediately. This can be a concern if planning on an extended road trip or an overseas adventure when you don't have access to a shower or laundromat. We must admit this is often the case with synthetics, and Merino wool is often our first choice for a naturally odor-free fabric. That being said, the smell would subside after washing with detergent. After hundreds of feet of off-width climbing, our testers are confident in the durability and construction of this affordable base layer.

Drying Speed

We recorded drying speed from several different testing angles, noting which layers dried quickly on the climbing rope, on the body, and air-dried overnight. The REI Co-Op Midweight is considered a midweight and performed accordingly. Our testers recorded a drying speed of 51 minutes after we dunked the layer in a local stream, wrung it out to dry, and tossed it on our climbing rope to dry in the spring sunshine.

Our testers also got moving and worked up a sweat, whether out on our skis or in our running shoes, for at least one hour before heading back inside to start the stopwatch and determine the drying speed on the body. The Midweight required only 38 minutes to dry on the body, taking the longest amount of time around our sports bra. To maximize the lifespan, we recommend allowing this layer to air dry overnight instead of exposing it to the heat of a dryer.

Layering Ability

Our testers love the thumb loop feature, which enhances this top's layering ability by holding it in place and preventing the sleeves from bunching up when pulling on a mid-layer fleece or jacket over the top. We also found that the polyester and spandex-blend fabric created a smooth surface that didn't grab other fabrics when layering.

While the Midweight is rather easy to layer underneath something, the slim fit prevents layering underneath with anything more than a tank top. When trying to layer anything with sleeves, we found it far too tight, thereby limiting breathability and range of motion.

Should You Buy the REI Co-op Midweight Base Layer Crew?

While this base layer doesn't perform as well as other synthetic layers in this review, our testers believe that you get what you pay for. Features like strategically placed flatlock seams enhance the overall comfort and durability of this layer. Additionally, it's available for a fraction of the cost of other synthetics while still providing enough warmth, thanks to a durable and stretchy fabric, as well as a slim fit that effectively traps body heat during moderate cold weather activities.

What Other Women's Base Layers Should You Consider?