The UltraBoost—Adidas’ most popular runner—has once again been updated & upgraded. The UltraBoost 21 retains a full-length Boost midsole but now has 6% more cushy foam than its predecessor. The shoe’s torsion system has also been juiced: it features LEP technology—Linear Energy Push—a 15% increase in forefoot rigidity for a more responsive stride. The upper is constructed with at least 50% Parley fabrics, comprised of upcycled ocean plastics.