With the help of 1.2 million foot scans, adidas updated Ultraboost with a complete 360° female fit improvement. And they didn't stop there. They re-engineered the rubber outsole. They tested hundreds of prototypes. They kept going until they saw visible improvements in performance. The result? 4% more forefoot energy return, compared to Ultraboost 21 for women. The adidas Primeknit upper includes a narrower heel fit, designed to avoid heel slip and blisters. You'll be riding on a Boost midsole with a Linear Energy Push system. The shoe's upper is made with yarn containing 50% Parley Ocean Plastic — reimagined plastic waste, intercepted on remote islands, beaches, coastal communities and shorelines, preventing it from polluting our ocean.