Find the perfect balance of cushioning and speed in the Karhu Fusion 4.5. Built to help you find your running rhythm, the Fusion 4.5 combines Karhu's responsive AeroFoam Nitro midsole with their signature compact Fulcrum technology to deliver the most pronounced "roll" in the Karhu collection. With smooth transitions at any pace and a geometry designed for exciting toe-offs, this trusted daily trainer is ready to tackle everything from long runs to tempo workouts. Details: Upper: The refined IdealKnit construction enhances breathability and comfort while maintaining a snug, streamlined fit. Broader laces and a soft, redesigned tongue give you a secure, premium feel that locks your foot in place. Strategic reflective detailing increases visibility during low-light runs. Midsole: The AeroFoam Nitro foam delivers responsive cushioning that feels both cushioned and quick underfoot. Combined with Karhu's compact Fulcrum technology, it creates an efficient, propulsive ride with smooth transitions that make every stride feel effortless. Outsole: Engineered with a geometry that supports dynamic toe-off, helping you maintain momentum through your gait cycle with confidence and control.