How do you improve on a running shoe that's all about energy return? Give it more energy return. The adidas Ultraboost 21 Shoes are super comfortable, so the extra miles and faster splits feel effortless. In addition to more Boost in the midsole, they have a Linear Energy Push system that feels like an extra push of energy in each step. This product is made with Prime blue, a high-performance recycled material made in part with Parley Ocean Plastic. 50% of the upper is textile, 75% of the textile is Prime blue yarn. No virgin polyester.