Caleb Olson won the 2025 Western States men’s ultra-marathon in June with the second fastest time in course history, and he also garnered a nontrivial amount of attention for the holey crop-top shirt he did it in.

Now, Nike ACG is ready to get the word out on that viral top, the Radical AirFlow, as well as the new Ultrafly trail super shoe.

Offering what Nike ACG is calling “radical cooling,” hence the name, the sweater-like top features cone-shaped airducts to increase the speed of airflow and boost the speed of sweat evaporation. These holes are placed strategically and vary in size in the mission of temperature management, as do dimples on the interior side.

Getting more scientific, it’s the Bernoulli principle and Venturi effect at work on the Radical AirFlow. The former is a concept explaining how a fluid (or air) increasing in speed will simultaneously decrease in pressure. The latter is the name for the phenomenon in which a fluid increases in speed when moving from one section of a pipe into another that’s smaller.

Western States was chosen as the race appearance for the Radical AirFlow because of the notorious heat in the 100-mile run. Perhaps somewhat counterintuitively, wearing the top makes you feel cooler than without it.

Aside from encouraging Airflow, the top also absorbs and retains 50 percent less sweat than other garments tested by Nike. It also has large cut-outs at the armpit and elbows, and is cropped so as not to block access to a running belt.

Olson and other ACG athletes were also wearing a prototype for the ACG Ultrafly, a successor to the original Ultrafly Trail from outside of the ACG line. Underfoot is ZoomX cushioning paired with a 7/8 length carbon fiber plate that’s less rigid than that on the original Ultrafly Trail and split down the middle for better torsional flexibility and control on uneven surfaces. A full-length ZoomX sockliner is also used for the first time in a trail-running shoe, and a wider last gives more room in the toe box, a boon as feet swell over the course of long runs.

A men’s size 10 comes in at 287 grams with a stack height of 37mm and a 4mm drop. The Vibram Lightbase outsole then comes with 3mm lugs.

Nike ACG conducted 13 rounds of testing on the UltraFly, accumulating more than 30,000 miles of running.

“Since the beginning of 2024, I’ve been racing in the Nike ACG Ultrafly,” Olson said. “It’s been my go-to, do-it-all racing shoe. It can handle some of the most rugged terrain I’ve raced on at Transgrancanaria, as well as the singletrack at Western States. It’s a great balance between all-day comfort and top-end performance that has helped put me on top of the podium at some of my biggest races.”

Both the Nike ACG Radical AirFlow and Ultrafly will release in spring 2026.