The trail ahead is rocky, steep, and covered with patches of snow and ice. I plunge forward, dropping from the ridge as sunrise crests over the Great Plains below. My feet hop from rock to dirt, and I wear a silly grin as I careen down the rustic trail. Yes, these wild-looking shoes can really grip. This is one fun descent.

One look and you’ll recognize that the first trail running shoe from Swiss brand X-Bionic is a departure from the norm. Called the TerraSkin X00/C, this trail running shoe has a prominent “Speedframe” wrapping the midsole, an aggressive outsole, and a shoe-specific sock. After a couple of weeks of testing, I agree with the brand in that this is a focused tool for aggressive downhill running and precise foot placements on technical trails.

In short: The X-Bionic TerraSkin X00/C is a precise trail running shoe for rocky, technical, and steep terrain. It leverages a carbon plate, as well as high-rebound EVA midsole cradled in a stiff “Speedframe” to provide a stable, very grippy shoe. While it sits on the heavier end of the trail running shoe spectrum, the TerraSkin X00/C is fast and secure, especially on technical descents. On the downside, it isn’t particularly lively underfoot.

Compare the X-Bionic TerraSkin X00/C with the best trail running shoes.

X-Bionic TerraSkin X00/C Review

To be entirely transparent, this is an early review. I’ve had the X-Bionic TerraSkin X00/C shoes to review for about 2 weeks now and have six runs in them. I will update this story once I have more distance in them. But for now, I wanted to share my impressions about this shoe as it’s a buzzing topic.

Spoiler — it’s good! But it is also a specialized tool. Let’s jump in.

Putting on the X-Bionic for the first time, you’ll also be putting on a new pair of socks. That’s because X-Bionic — mainly known for its running, cycling, and winter sports apparel and socks — built the TerraSkin line from the sock out. So, each pair of shoes ships with an included pair of TerraSkin Socks.

The socks fit snugly and are relatively thin. The left and right socks are asymmetrical and have thicker ribbing to support the Achilles tendon and instep. Mine are also different colors, as are the shoes in their bright pink and white or black. Talk about making a statement!

Ultimately, these socks grip the skin well and provide a secure fit inside the shoes. With an ultimate goal to provide secure footing on rough trails, the sock is a good place to start.

Above the foot is a stretchy yet tough upper. The middle of the upper, along the laces, combines stretchy fabric with stable TPU on the sides, which then links to the Speedframe. The result is a pretty snug upper that keeps your foot from shifting inside the shoe. I really like the fit, which is very comfortable yet secure.

In my test runs, I tried pretty hard to make my foot slop around in the shoe, and it simply didn’t. Even though the shoe isn’t exactly tight fitting, the design hugs my foot well, keeping it engaged and locked within the shoe.

I think that’s good because the midsole’s unique design is both responsive and directional. It doesn’t allow the foot to roll sideways much, even on sharp rock edges or uneven terrain. So, the foot really needs to stay snugly inside this upper.

Finally, let’s talk outsole. These are really grippy shoes with relatively deep lugs. X-Bionic calls this Vibram design “Spinweave.” Basically, rubberized nubs sit on the outside of the Speedframe. The brand claims this design increases surface area by 27% compared with other outsoles.

In practice, I found the outsole grippy on rock, dirt, and frozen ground. It’s even decent on packed snow. I haven’t tested it on wet surfaces yet, but I suspect it’ll perform.

So, put all this together, and what do you have? This shoe is a downhill weapon, ready for some wild descents.

Testing the X-Bionic TerraSkin X00/C

The loop around Matthews/Winters Park and Dakota Ridge outside Denver is a trail runner’s dream. Steep climbs, fast flats, and lots of technical rock sections challenge any trail runner to keep upright. Having run this trail maybe hundreds of times over the last 10 years, I have quite a few scars to memorialize some spectacular crashes. So, it seemed a great testing ground for the X-Bionic TerraSkin X00/C.

Let’s start with the wins: The X-Bionic TerraSkin X00/C runs downhill like a well-balanced sports car. With fast footwork between rocks and dirt patches, I found myself locked into the ground.

Change direction on a boulder, and the shoe locked on the placement, propelling me quickly with a lot of energy return and a good ground feel. My foot stayed locked into the capable upper. And the outsole gripped well on everything from frozen ground to dry rock. The TerraSkin X00/C is wonderful in that kind of tricky terrain, especially on descents.

Where It’s Not So Good

The TerraSkin X00/C is less exciting on longer, flat sections of rolling dirt trails. There, it’s an entirely capable trail running shoe. The midsole is protective. But while it does give modest rebound, and I moved along at a good clip wearing them, they’re relatively muted on the flats. To be clear, the X00/C is a little clunky when the road gets smooth.

I did run these on a couple of morning city runs, and as expected, it’s not great on pavement. Like a pickup truck with 35-inch tires, this shoe is not optimized for concrete or smooth trails.

This is not a road-to-trail shoe. Don’t expect zippy, low-impact performance on tarmac. The X-Bionic TerraSkin X00/C is a focused tool for trail and dirt running. Sure, you can run it on pavement or smooth trails. But it does not excel there.

One more important point on this shoe: It’s expensive, retailing at $300. However you cut it, that’s a heavy hit for a running shoe.

Who Should Run in the X-Bionic TerraSkin X00/C?

After several outings, I feel like I have a good sense of this very cool trail running shoe. I’m glad I have a pair and see it as a pretty specialized tool.

Until I test it more, I’d recommend the X-Bionic TerraSkin X00/C as a trail running shoe for those who cover lots of technical terrain and want a precise shoe. It excels at fast descents and should be a great fast hiker, too, as the grip is absolutely fantastic.

I also think it could be a good fell runner, as it has really aggressive lugs that should dig into soft soil well. But if you mix road and trail running or want a lightweight shoe that can transition between the two, look elsewhere. This is a specialized tool.

That’s not a bad thing. If you’re looking for a grippy trail runner for those spicy sections, check it out. The X-Bionic TerraSkin X00/C is a compelling, fun shoe that will help flesh out the quiver of the avid trail runner.