It has a   stack height   of 33 mm in the heel and 28 mm in the forefoot, with a   5 mm   drop. Designed for long trail runs at almost any pace, it features an updated ZipFoam midsole with a 3 mm   stack increase , a   breathable mesh upper , and a reliable Vibram Megagrip outsole. On the run, it provides unbeatable traction and great ZipFoam energy return, though it may feel a bit too roomy.