The adidas Women's Ultraboost 21 Running Shoes are the latest in an impressive line of innovation. Evolving over time from constant testing and feedback, the design of this running shoe has been completely overhauled for 2021. Offering a sock-like fit thanks to the stretchy and breathable Primeknit+ upper, padded collar and integrated tongue, while a heel counter and supportive midfoot cage provide security and a precision feel. The midsole has more boost than its predecessors - cushioning impact shock for an incredibly comfortable ride and working in synergy with the LEP Torsion System to give a stable transition through to a high energy toe-off. Finally, an updated Stretchweb outsole with Continental Rubber ensures long-lasting durability and grip. Boost Energy With 6% more Boost capsules present in the midsole, this current iteration in the Ultraboost series creates a softer underfoot feel that explodes with forward propelling energy. LEP (Linear Energy Push) Torsion System Delivering incredible energy return, the LEP Torsion System supports the midfoot for a smooth transition and provides a 15% increase in forefoot bending stiffness for a more responsive run. Recycled Primeblue materials Made with Primeblue - a high-performance recycled material made in part with Parley Ocean Plastic. 50% of the upper is textile, 75% of the textile is Primeblue yarn and no virgin polyester has been utilised making this the most sustainable Ultraboost model to date.