PRONATION: Pronation is part of the natural movement of the human body and refers to the way your foot rolls inward for impact distribution upon landing. Understanding your pronation type can help you find a comfortable running shoe. The GEL-NIMBUS 21 is made for Neutral and Underpronation.FLYTEFOAM LYTE TECHNOLOGY: ASICS lightest weight midsole formulation that provides continuous cushion thanks to organic nano fibers.I.G.S (IMPACT GUIDANCE SYSTEM) TECHNOLOGY: ASICS design philosophy that employs linked componentry to enhance the foot’s natural gait from heel strike to toe-off.ORTHOLITE X-40 SOCKLINER: This premium sockliner features higher rebound properties while providing excellent moisture management and a high-level of breathability (Ortholite is a registered trademark of ATP Manufacturing LLC.)AHAR OUTSOLE: Acronym for ASICS High Abrasion Rubber. Placed in critical areas of the outsole for exceptional durability.