Spira Del Sol Women Mesh / Polyurethane Cushioning Technology: WaveSpring--Provides cushioning and energy return while centering the foot during the stride. Heel Technology: WaveSpring--Returns energy with every step and is light, compact, and durable. WaveSpring provides a superior blend of cushioning through deflection of the steel alloy spring midsole system combined with efficient energy return for optimal performance. Lacing System: Traditional Lacing System--Traditional lacing system provides a tighter fit for more centralized support. Model Number: SLT522 Recommended Fit: These shoes run True to Size.