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Nike ACG Ultrafly – lateral view – Caleb Olson 2025 Western States 100 pair

The lateral view of the Nike ACG Ultrafly prototype that Caleb Olson wore to win the 2025 Western States 100. Photo courtesy of brand.
By on August 24, 2025 | Comments
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Nike ACG Ultrafly - lateral view - Caleb Olson 2025 Western States 100 pair

Bryon Powell

Bryon Powell is the Founding Editor of iRunFar. He’s been writing about trail running, ultrarunning, and running gear for nearly 20 years. Aside from iRunFar, he’s authored the books Relentless Forward Progress: A Guide to Running Ultramarathons and Where the Road Ends: A Guide to Trail Running, been a contributing editor at Trail Runner magazine, written for publications including Outside, Sierra, and Running Times, and coached ultrarunners of all abilities. Based in Silverton, Colorado, Bryon is an avid trail runner and ultrarunner who competes in events from the Hardrock 100 Mile just out his front door to races long and short around the world, that is, when he’s not fly fishing or tending to his garden.