We have redesigned the core form and developed a new core material that is stable, solid, hard, dimensionally stable. Made with high shape accuracy. The core is first applied to the middle - soft PU layer, which perfectly dampens vibrations. The outer hard layer provides low rolling resistance and low wear. Thanks to the outer, direct contact of the core with the harder PU layer, the rebound energy is effectively transferred to the forward movement. This is achieved by the fact that bumps, unevenness must be damped in the range of micro seconds, while the rebound (although more dynamic in tens of micro seconds).