Many runners have found that the Altra Duo is a bit deceptive. It has the look of a heavy shoe, but it weighs a mere 7.9 ounces. The outsole features blown rubber for great durability, and the midsole offers Max-LT cushioning to keep you comfortable on race day. The padded tongue only adds to the secure fit and cozy interior. The rest of the upper has thin and breathable mesh, so your feet won't feel overheated as you push yourself to new limits.