Prototype after prototype. Innovation after innovation. Testing after testing. Meet us in the hot pursuit of the pinnacle harmonization of weight, cushioning, and responsiveness. Ultraboost 21. Say hello to incredible energy return. The new adidas LEP Torsion System provides a 15% increase in forefoot bending stiffness for a more responsive run. Ultraboost 21 has 6% more Boost capsules ready to explode with energy in each step. This product is 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. No virgin polyester.