Polished again and again, innovated again and again, tested again and again, in order to integrate fashion, comfort and technology. adidas Ultraboost 21 helps you feel the comfort of sports. The Ultraboost 21 is innovative with a Stretchweb grid bottom and Continental horse rubber in specific areas. The outsole is lightweight and flexible, and strives to adapt to a variety of climates and the ground to keep you moving with ease. Primeknit+RORGED upper design is not designed to bring elasticity where necessary. The heel has a pouch inside for a sock-like fit and prevents slipping heels. The full-palm BOOST technology midsole has a 6% increase in Boost material content compared to Ultraboost 20.