adidas Ultraboost Running Shoes Primeknit upper - Wraps the foot in adaptive support and ultralight comfort. Supportive cage - Locks down the midfoot. FitCounter - Moulded heel counter provides a natural fit that allows optimal movement of the Achilles. Boost Midsole - Has an amazingly bouncy feel without being too soft, and that makes for a light, fast run. Torsion System - For a stable ride.