Bootie upper construction hugs your foot for a snug, supportive fit Fresh Foam midsole cushioning is precision-engineered to deliver an ultra-cushioned, lightweight ride Upper features a breathable yet protected construction Vibram Megagrip outsole provides superior grip There's more to off-road running than fresh air and scenic views. Uneven terrain, debris, moisture, to name just a few of the challenges you'll face. New Balance clearly get it. That's why they've designed Hierro here, a dedicated, off-road trainer with the brand's best running technology.