The Nike ACG Ultrafly is a cushy, responsive, and stable shoe designed for long-distance running and ultra-distance racing on a variety of surfaces.
Nike made waves when it launched its original Ultrafly trail running super shoes in 2023, but not necessarily because it had a carbon-fiber Flyplate or a hyper-responsive version of ZoomX midsole foam from Nike’s top-tier marathon racing shoes. The thing that really changed the game for Nike with that shoe was the use of a Vibram Megagrip outsole for the first time, giving the shoe best-in-class grip on a wide range of surfaces.
Before it retooled that shoe and launched the ACG Ultrafly this past winter, Nike ditched its Nike Trail branding in favor of All Conditions Gear, aka, ACG. More than just a naming convention, ACG is a youthful brand segment that’s more loosely associated with mainstream outdoor interests like hiking, camping, snowboarding, and basic bouldering rock climbing. Why did that happen and why is it relevant for a trail running shoe? Like a lot of brands, Nike sees huge growth in trail running and it really wants to tap into the growing segment of Gen Z trail runners and all types of trail-curious outdoorsy types.
That was pretty evident in Nike’s promotions around the 2026 Winter Olympics in Italy, and having Mikaela Shiffrin wear a pair of these fluorescent orange kicks on the podium after winning the gold medal in the women’s slalom was icing on the cake. (Fortunately, Nike has dropped several other colors of the ACG Ultrafly since the original launch color debuted last winter.)
The good news is that, marketing and other sports aside, the ACG Ultrafly is a very good trail running shoe, ideal for long-distance running and ultra-distance races on a variety of surfaces. The maximally stacked ZoomX midsole serves up a lot of energy return (especially at faster paces on smooth trails and gravel roads) along with improved impact protection, and it’s left partially exposed under the shoe so the foam can help a runner’s foot placement adapt naturally to uneven terrain.
One of the best changes to this version of the Ultrafly is the new, slightly more flexible iteration of the carbon-fiber Flyplate, which now runs most of the length of the shoe and has a split in the middle that allows it to moderate the torsional rigidity and create a more stable base on uneven trail terrain.
Nike put this race-ready shoe through 13 rounds of testing and logged 30,000 wear-tester miles in its development, and as a proof of concept, Nike athlete Caleb Olson won the 2025 Western States 100 in the second fastest time in history wearing a prototype version of it. More recently, Jennifer Lichter wore a pair in her runaway win at the Black Canyon Ultras 100K in February.
When you’re running on trails or gravel roads, you’ll feel a moderate energetic pop from the midsole as you roll through to the toe-off phase of a stride. However, it feels more controlled and structured (and much less bouncy) than what you typically get from a Nike road racing shoe. Perhaps best of all, for such a maximally cushioned shoe with such a wide footprint, it actually feels both stable and somewhat agile without being inhibited (like some other carbon-plated trail shoes), and that allowed me to tackle some technical terrain with confidence.
RELATED: Find Your Next Trail Running or Ultra Race
Nike ACG Ultrafly Specs
Price: $260
Approximate Weights: 8.4 oz. (women’s size 8), 9.8 oz. (men’s size 9)
Heel-Toe Offset: 8.5mm; 38mm (heel), 29.5mm (forefoot)
Key Features: The Nike ACG Ultrafly features a breathable, quick-draining mesh upper paired with a trail-tuned fit that creates a secure, comfortable lockdown for long runs across varied terrain. Its ZoomX midsole, combined with a carbon-fiber plate, delivers significant energy return and smooth propulsion to help runners stay efficient and reduce fatigue. The Vibram Megagrip Litebase outsole, along with a slightly more flexible plate design, improves traction and control, boosting confidence on technical and uneven trails. Also of note: this shoe doesn’t have that classic Nike fit (typically relatively narrow and snug) and instead has more of a medium-volume fit with a modest amount of wiggle room in the toe box.
Why You’ll Probably Like This Shoe: You can consider this either a refined update of the original Nike Ultrafly, or you can consider it a really great new trail running shoe. While some of the features remain nearly the same or similar (Zoom X midsole, 8.5mm heel-toe offset, and a Vibram outsole), just everything about the new version is better. It’s a lighter, cushier, more durable, and more stable shoe than its predessor for long-distance running on a variety of surfaces.
Why You Might Not Like This Shoe: It’s not exceptionally light or nimble, so if you’re looking for a shoe for short and fast mountain running or dancing through technical terrain, you might want to look elsewhere. (The more experienced of a trail runner you are, the more capable the shoe will be on technical terrain.) Also, there were times I felt the outsole could have benefited from slightly deeper lugs. While it performs well for its intended terrain, grip can feel less secure on softer surfaces such as mud, loose gravel, sand, or snow.
Pros: The best aspects of this shoe are its long-haul comfort, high-performance ride and the stride efficiency it allows for multi-hour runs on a variety of types of trail surfaces. It’s best on gravel and dirt roads, smooth trails and mildly technical terrain.
Cons: As with many other shoes (including the previous Nike Ultrafly), this shoe has an outsole with low-profile lug depth. That’s great for most types of terrain, but it can still result in slippery situations in wet or sticky mud or deep gravel and loose scree. Also, some runners might find the Flyplate to be too stiff to provide the agility they’re seeking in a trail running shoe.
Check it out at Running Warehouse → Nike ACG Ultrafly (Unisex Sizing)
RELATED: Find Your Next Trail Running or Ultra Race
About the Author
UltraSignup Director of Media Brian Metzler was the founding editor of Trail Runner magazine, has written for Runner’s World, Outside, and Sports Illustrated, and is the author “Kicksology: The Hype, Science, Culture and Cool of Running Shoes” (2019) and “Trail Running Illustrated” (2021). He has raced just about every distance from 100 meters to 100 miles, but he’s most eager to share stories about his experiences pack burro racing in Colorado and riding trains to run trails in Chamonix, France.
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