With the help of 1.2 million foot scans, we updated Ultraboost with a complete 360Â° female fit improvement. And we didn't stop there. We re-engineered the rubber outsole. We tested hundreds of prototypes. We kept going until we 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 PlasticÂ reimagined plastic waste, intercepted on remote islands, beaches, coastal communities and shorelines, preventing it from polluting our ocean.