The Altra Lone Peak 9 builds on a proven thru-hike platform with a reengineered upper, revised midsole foam, and an updated outsole. The 100% RPET ripstop mesh moves air across long back-to-back days, the lighter Altra EGO foam keeps the ride cushioned without adding bulk, and the FootShape last gives the foot room to work naturally from the first mile to the last. What Our Gearhead(R) Experts Are Saying:"The zero-drop stack keeps my foot flat and my stride natural over long miles. On a thru-hike day where I'm covering 20-plus miles, that geometry is what keeps my calves from seizing up by afternoon."