Huaraches are a tight fit because of the strap at the back, more so than the length of the shoe. If you measured the length it would probably be the right size it says, but the plastic strap at the back doesn't really stretch that much and that's why they run smaller.

With its stretchy, foot-hugging fabric and futuristic heel cage, it's still everything you love about the Huarache. Inspired by water skiing, the stretchy upper and cushioned inner sleeve create a snug fit for an incredible feel. Originally designed for performance running, Nike Air cushioning delivers lasting comfort.

The Nike Air Huarache released in 1991. Footwear designer Tinker Hatfield wanted to combine the fit of neoprene water-ski boots with the functionality of South American sandals. The instant hit found its way to basketball courts and then the streets, where it earned its status as an icon.