*updated*full-length dual density midsole - a soft top layer of eva that creates comfort and cushioning. the midsole layer underneath has a higher density of solyte material that gives stability and responsiveness. *new* fluidaxis - adds uniquely positioned deep flex grooves in the outsole to allow for a more natural motion of the subtalar joint so that you feel more comfortable underfoot, while you run. *updated* lightweight - at 290g, the all new gel-excel 33-2 is lighter than its predecessor. impact guidance system (i.g.s.) - asics design philosophy. employs linked componentry that enhances natural gait from heel strike to toe-off. heel clutching system - exoskeletal heel counter in the shoe provides improved supprt and an improved heel fitting environment for the serious runner.