We designed a new core last and found new core material that is stable, solid,
tough, shape-stable. It can be injected in high shape precision. The core is
firstly applied to the center-soft PU layer, which greatly dampens the
vibrations. The outer hard layer provides low rolling resistance and low wear.
Through the external - direct contact between the core and the harder PU layer,
the push off energy is effectively transmitted forward. This is achieved by the
fact that the bumps from the inequalities have to be damped in the range of
microseconds, while the push off (even the most dynamic is in the range of tens
of microseconds). The set contains 6 wheels.