Reviews You Can Rely On

REI Co-op Active Thong Review

The affordable price tag is alluring, though our testers were disappointed by the fit, durability, and longer drying time
rei co-op active thong travel underwear women review
Credit: REI Co-op
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Price:  $15 List
Manufacturer:   REI Co-op
By Trish Matheny ⋅ Review Editor  ⋅  Jul 13, 2021
  • Comfort - 35% 7.0
  • Fit - 30% 8.0
  • Drying Time - 25% 5.0
  • Packability - 10% 9.0

Our Verdict

At first glance, we had high expectations for the REI Co-op Active Thong as it was the only synthetic thong that we tested. While we like the softer fabric, flattering waistband, and frontal coverage, we were ultimately disappointed that the liner is 100% cotton, a material that does not dry quickly. We were also psyched to try a more affordable option but were quickly disappointed when we noticed the flatlock seams begin to unravel after minimal wear. These quality issues made it difficult for us to recommend this garment out of fear it could fall apart during extended travel.
Nice waistband
Not very durable
Flatlock seams unraveling with minimal wear

Our Analysis and Test Results

The REI Active Thong is a synthetic option at nearly a third of the price of its wool competitors. This garment is ultralight, weighing only 0.42 ounces. The material is soft and breathable but we were disappointed by the 100% cotton liner that increased the amount of time it took to dry on the line.

Performance Comparison

rei co-op active thong travel underwear women review - the synthetic blend fabric of the rei active thong is silky smooth...
The synthetic blend fabric of the REI Active Thong is silky smooth and soft to the touch.
Credit: Trish Matheny


Comfort is perhaps the most important category when selecting a pair of underwear for a long road trip or an extended period in the backcountry. So we put these undies to the test by identifying the type of material and thickness of each garment, how that material feels on the body, whether it's soft or itchy, and finally how well the material breathes.

The Active Thong scored high marks for its overall breathability, performing well during trail runs and hot yoga classes. Constructed from 86% polyester, 14% Spandex, and a 100% cotton liner, this thong is silky smooth. However, we noticed that the flatlock seams of the garment lacked a bit of comfort and caused us to adjust ourselves due to itchiness while trying to log our miles.

rei co-op active thong travel underwear women review - most of the undies that we tested made it easy to remove the tag in...
Most of the undies that we tested made it easy to remove the tag in order to increase comfort.
Credit: Trish Matheny


Fit is such an important component when selecting a new pair of travel underwear. It truly doesn't matter how well the material performs if you are constantly distracted by how your undies fit your body. For this metric, we compared each cut, from thongs to hipkinis, to evaluate and score which model fit our bodies the best, whether or not the material provided the appropriate amount of stretch to move with us while assessing whether or not the waistband did its job to hold the garment in place.

In our opinion, the thicker waistband is flattering but didn't quite hug our hips as we would like. And while the material offers a lot of stretch, we were disappointed that the stretch prevented the material from forming to our bodies. The Active Thong features a great, full-coverage fit that we love but the waistband lacked the ability to hold this garment in place during activity.

rei co-op active thong travel underwear women review - we loved the stretchy fabric of the active thong that allowed us to...
We loved the stretchy fabric of the Active Thong that allowed us to move freely in the mountains.
Credit: Trish Matheny

Drying Time

Our testers understand how important it is for travel underwear to feature a breathable material that dries quickly, whether due to hard-earned sweat or a quick hand wash in a nearby stream. So besides washing these undies during our backcountry adventures, we also conducted a more scientific test on a partially sunny spring day in Victor, Idaho to determine how quickly each garment would dry on the line after being soaked in water and wrung out by hand.

We had high expectations for the Active Thong, considering its synthetic exterior; however, with a dry time of 50 minutes, it was hardly competitive. The reason likely lies with the liner. The liner is 100% cotton and we attribute the longer drying time to the less breathable cotton fabric. Even though it was dry in less than an hour, it fell short when compared to other thong models that we tested in this category.

rei co-op active thong travel underwear women review - the rei active thong took the longest to dry out of the three thong...
The REI Active Thong took the longest to dry out of the three thong cuts that we tested.
Credit: Trish Matheny


Although underwear does not take up much space when compared to bulky climbing gear or thick puffy jackets, weight and overall compactness are significant factors to consider, especially when attempting to go ultralight in the backcountry. For this metric, we took out our scales and weighed each garment before comparing all the undies side by side to assess the amount of space they required in our luggage.

It is easy to give the Active Thong high scores here. It's less than half an ounce and packs down very small. The difference between the space each thong required in our backpack was negligible; however, if trying to go as light as possible, this is a garment to consider for your next adventure at just 0.42 ounces.

rei co-op active thong travel underwear women review - weighing just 0.42 ounces, the rei active thong is an ultralight...
Weighing just 0.42 ounces, the REI Active Thong is an ultralight option.
Credit: Trish Matheny


The Active Thong is one of the most affordable, athletic thongs available; however, you get what you pay for. The quality of this garment was noticeably lacking when compared to the more expensive wool options and the only garment to show significant signs of wear during testing making it difficult for us to recommend this model to perform well during travel.


While we wanted to love the REI Co-op Active Thong because of its affordable price tag, it was very clear to us after significant testing that it lacked the quality and performance of other superior options available.

rei co-op active thong travel underwear women review - while the rei active thong scored well in some metrics, the overall...
While the REI Active Thong scored well in some metrics, the overall quality was a deal breaker for us.
Credit: Trish Matheny

Trish Matheny
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