The second edition of the Asics GEL-HYPER33 continues to innovate with technology that helps you run more naturally. The GEL-HYPER33 2 introduces the new Fluid Axis, adding uniquely positioned deep flex grooves in the outsole to allow for a more natural motion of the subtalar joint. This edition also contains an extended Propulsion Trusstic. Mimicking the plantar fascia in the arch of your foot, it assists your foot in propelling you forward. The Full Length Guidance Line along the outsole promotes a more efficient gait from foot down to toe off. The heel contains Rearfoot GEL for great cushioning, while the Dual Density Midsole, made from an EVA top layer & a Solyte layer, create a great balance of cushioning, stability & responsiveness. Specifications: Shoe Category Natural Barefoot Running Ideal Use Barefoot Running Weight Approx. 290 grams Glossary: Fluid Axis Allows for a more natural motion of the foot by letting the subtalar joint rotate around its axis. Rearfoot GEL Cushioning Systems Attenuates shock during impact & toe-off phases & allows movement in multiple planes as the foot transitions through the gait cycle. Guidance Line Vertical flex groove decouples the tooling along the line of progression for enhanced gait efficiency. Full Length Dual Density Midsole A soft top layer of EVA that creates comfort & cushioning. The midsole layer underneath has a higher density of Solyte material that gives stability & responsiveness. Propulsion Trusstic Mimics connective tissue in the foot by creating tension as foot enters propulsion stage. AHAR Acronym for ASICS High Abrasion Rubber. Placed in critical areas of the outsole for exceptional durability.