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Luna Oso Flaco Winged Review

For those curious about minimalist running, this sandal offers superior traction and secure straps that will keep you comfortable on the trail
Top Pick Award
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Price:  $110 List | $105.00 at Amazon
Pros:  Great traction, secure straps, lightweight
Cons:  Uncomfortable, difficult to adjust, questionably stylish
Manufacturer:   Luna
By Joanna Trieger ⋅ Review Editor  ⋅  Jun 16, 2020
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70
OVERALL
SCORE


RANKED
#8 of 14
  • Comfort - 20% 5
  • Traction - 20% 9
  • Adjustability - 20% 7
  • Stability - 15% 8
  • Versatility - 15% 6
  • Style - 10% 7

Our Verdict

If you've been itching to get into minimalist trail running but weren't sure where to start, we've got you: pick up a pair of the Luna Oso Flaco Winged. This pared-down, thin-soled model provides enough protection to keep trail running comfortable while still giving the wearer a real sense of the ground beneath her feet. After dozens of miles loping up and down rocky single track and crashing through streams, we can report that the Oso Flaco really holds up, earning it our Top Pick for Minimalist Trail Runners Award. Beyond running, though, this model isn't our favorite for comfort, versatility, and style, so we don't recommend it as an all-around pick.

Compare to Similar Products

Our Analysis and Test Results

Have you read Born to Run? Wondering what Barefoot Ted has been up to since his foray into the Copper Canyons? Well, wonder no more: we're here to report that Ted put his wacky brain to work creating a minimalist footwear line, Luna Sandals, so the rest of us can experience the joys of running free. Intrigued, we added the Luna Oso Flaco Winged to our testing lineup to see how it stacked up. While this model isn't comfortable, versatile, or stylish enough to get an all-around thumbs up, its outstanding traction and secure strap system make it an excellent introduction to barefoot trail running. Read on to see if you're ready to make the leap, but be warned: you may never go back!

Performance Comparison


The Lunas in their natural environment: the mountains!
The Lunas in their natural environment: the mountains!

Comfort


This extremely minimalist sandal doesn't put a lot of material between you and the ground, so it's not the most comfortable model we tested.


The Oso Flaco is meant to mimic barefoot running, so it doesn't have many features we'd describe as "comfortable." Its sole is thin and flexible, so you feel every lump and bump in the ground as you walk or run. Its straps are also thinner than most of the other models we tested, and they need to be tightened significantly to achieve a secure fit, so they tend to dig into the skin. The semi-firm rubber elements on the sides of the foot that the straps pass through are fixed in place, so if they happen to hit your foot in an uncomfortable spot — as they did for our lead tester — you're in for an uncomfortable ride.

This model's thin straps and fixed-in-place side-foot attachment points make it a less-than-comfortable hiking option.
This model's thin straps and fixed-in-place side-foot attachment points make it a less-than-comfortable hiking option.

This model truly is designed for running, and we found that something about the running motion made the Oso Flaco Winged feel more comfortable. When running, the foot tends to move back against the heel strap, which distributes the pressure better between the thin straps and aligns the foot better with the rubber elements that hold the straps. So, surprisingly, this generally uncomfortable model becomes one of the most comfortable while running.

One major point of discomfort we have to mention: the lugs at the sides of the out-of-the-box Lunas are so sharp that if you happen to catch your opposite ankle with the side of your sandal mid-stride, you may be in for a nasty cut. Help us out and file down those side lugs a touch, Luna!

Yikes! Our tester sustains a small flesh wound after brushing her ankle with the Luna's sharp lugs on the trail.
Yikes! Our tester sustains a small flesh wound after brushing her ankle with the Luna's sharp lugs on the trail.

Traction


Designed for steep, uneven trails and river crossings, the Oso Flaco excels in this category.


The Oso Flaco has deep, strategically placed lugs and a super-thin, flexible sole. This allows it to conform to pretty much any trail feature with an insane monkey grip. We tested this model on steep, loose dirt, slick rock, cobbled trails, and river crossings, and it performs admirably in each of these scenarios.

This is one of the most tractioned models we tested. We trust the Luna's deep-lugged Vibram sole on virtually any surface.
This is one of the most tractioned models we tested. We trust the Luna's deep-lugged Vibram sole on virtually any surface.

This model is especially excellent in water because the thin sole allows you to use your toes to grip rocks for extra stability. On the downside, the footbed gets pretty slippery when it's wet. When you emerge from the river crossing and continue down the trail, you'll slosh around in the sandal for a bit until things dry out.

The Oso Flaco's outsole is outstanding in watery environments  but unfortunately  the footbed gets slippery when wet.
The Oso Flaco's outsole is outstanding in watery environments, but unfortunately, the footbed gets slippery when wet.

Adjustability


With one flow-through strap and several adjustment points, it's possible to dial in the fit of the Oso Flaco, but doing so requires trial-and-error and on-the-go adjustments are tough. This model scored in the middle of the pack in this category.


The Oso Flaco has a single flow-through strap that starts between the toes, loops around the back of the foot with two rubber elements on the sides of the foot as guides, and then reattaches to itself with an adjustable buckle on the top of the foot. This means it's possible to adjust the length of the heel strap by pulling more or less strap through the side-foot elements. The positioning of the top-foot buckle can also be changed by sliding it back and forth along the strap, and the tightness of the whole sandal is adjusted by cranking down on the cross strap.

Adjusting the Lunas on the fly using these top-foot buckles is relatively easy. Dialing in the overall fit right out of the box takes some trial and error.
Adjusting the Lunas on the fly using these top-foot buckles is relatively easy. Dialing in the overall fit right out of the box takes some trial and error.

If this sounds like kind of a pain, that's because it is. It's possible to dial in the fit of the Oso Flaco, but it takes trial-and-error, and each adjustment to the heel strap necessitates removing the sandal. The rubber elements and the top-foot buckle are stiff, so pulling the strap through takes force. On the upside, once the sandal is adjusted to your foot, the straps tend to stay put, so you'll only have to do this once. During runs, you can easily make the whole sandal tighter or looser by tightening or loosening the cross strap.

Unfortunately, the rubber elements on the side of the feet are fixed in place, so if they don't fit your foot's anatomy, there's not much you can do about it. We'd love this sandal more if these could be angled to fit a wider variety of foot shapes.

Stability


With a supple sole and secure straps, the Oso Flaco feels stable on a wide variety of terrains.


The sole of the Oso Flaco is extremely flexible, so it contours to the terrain and helps the wearer feel stable. The footbed is wide, but the straps are secure, so the foot stays centered in place. While running, we found this model to be more stabilizing than even our thick-soled, crazy-lugged trail shoes.

The sole of this model is thin enough that it can contour around rocks  which adds a feeling of stability on the run.
The sole of this model is thin enough that it can contour around rocks, which adds a feeling of stability on the run.

We can't emphasize enough that the sole of the Oso Flaco is thin. While wearing a pack or otherwise carrying a heavy load, it can feel unsupportive, almost like you're walking…well, barefoot. If you're looking for a model that will feel cushy and supportive while you're carrying a pack, consider something with a thicker-sole.

Two approaches to stability: The thin-soled Luna  left  allows the wearer to contour to uneven terrain  while the Bedrock  right  absorbs the lumps and bumps of the trail.
Two approaches to stability: The thin-soled Luna, left, allows the wearer to contour to uneven terrain, while the Bedrock, right, absorbs the lumps and bumps of the trail.

Versatility


This sandal is great for running! We'd also recommend it for running, and while we're at it, have we mentioned running? We love the performance of the Oso Flaco as a trail runner, but it's not the sandal we choose for most other applications.


Our first impressions of the Oso Flaco weren't great. This model is not super-comfortable out of the box, and after an initial hike, we were ready to relegate these to the "quirk over quality" pile. But since these are clearly meant to be trail runners, we thought we should at least try to take them for a spin…and just like that, our lead tester was hooked. This sandal opens up and embraces the foot while running in a way it doesn't seem to do on hikes or jaunts around town. So if you've been curious about minimalist/sandal running, we'd strongly recommend giving these a try.

Running in sandals allows your toes to spread out and encourages a forefoot strike  which can improve posture. Our lead tester got hooked on running in Lunas after just one run.
Running in sandals allows your toes to spread out and encourages a forefoot strike, which can improve posture. Our lead tester got hooked on running in Lunas after just one run.

But for most other applications, the Oso Flaco falls short. It's not comfortable enough to be a regular hiker, it's not supportive enough for backpacking, and its soles are too flexible for all but the most casual bike rides. If you're looking for the one sandal to rule them all, look elsewhere.

The Oso Flaco is flexible and comfortable enough to wear during your post-run stretch routine. Canine assistants not included!
The Oso Flaco is flexible and comfortable enough to wear during your post-run stretch routine. Canine assistants not included!

Style


With its unique shape and technical feel, the Oso Flaco either suits your taste or it doesn't.


No one is going to mistake this for a fashion sandal: the Oso Flaco looks like it was designed by outdoor gear enthusiasts for use on the trails. Our testers and the friends and family we surveyed had mixed reactions to the look of this model, but feelings were generally positive, especially among trail-lovers. The Oso makes a unique accompaniment to a casual jeans outfit, but it would probably look out of place with anything dressier.

This model has a decidedly technical feel. We show them here covered in mud  as befits a great trail running shoe.
This model has a decidedly technical feel. We show them here covered in mud, as befits a great trail running shoe.

This model comes in several patterns and solid black, so you can coordinate with your favorite trail running gear if you're so inclined.

Value


A pair of dedicated trail running shoes will generally cost you a good deal more than these sandals, so if you're considering this model to replace or extend the life of your favorite traditional trail model, it's a good deal. Based on the extremely minimal wear and tear we observed after about 65 miles of trail running and dozens of miles of other activities, we think this pair will last well beyond the 500 miles we'd expect out of a regular trail trainer. We personally don't recommend the Oso Flaco for much beyond trail running, so if you're looking for an all-around sandal, this may not be a good value. That said, there are many folks that do wear these for hiking and around town. As with anything, it all depends on your anatomy and personal preferences. Because of the oddities of this sandal, however, it's one we recommend trying on before buying if you can.

Conclusion


So what do you think — are you ditching your Altras and going "barefoot"? As our Top Pick for Minimalist Trail Runners, the Luna Oso Flaco Winged is a unique option that offers enough protection to keep you comfortable on the run while still letting you feel the earth beneath your feet. If you want a single sandal that will take you from trail to bike to bar patio, this may not be it, but if minimalist running is your main goal, we think you should give this model a try.

Great traction  unique design  solid stability...will these Lunas lure you into minimalist running?
Great traction, unique design, solid stability...will these Lunas lure you into minimalist running?

Joanna Trieger