The Agility Peak Flex excels on the steep, rocky, and muddy trails that one of our editors runs above Boulder every weekend. “My heel stays locked in place when I descend, and it never feels sloppy when I move laterally,” he says, crediting the plastic heel molding and integrated “double-lacing” system for the secure fit. The laces bind the upper to the tongue, providing a snug feel without pinching. Traction and midsole cushion are about average for the category, but the breathable mesh uppers and nimble feel make them a good choice for backpackers who prefer trail runners for summer hiking with a light load. (If that’s you, check fit: Our wide-footed tester says he prefers more space in the toebox for all-day comfort with a pack on.) Tradeoff: Low weight and mesh uppers mean reduced durability.