The ULTRA's unique resistance unit provides a feel that's smoother and more realistic than anything else on the market. To simplify things, other trainers are speed sensitive; as long as the rear wheel is spinning, the trainer will provide a given degree of resistance per a given wheel speed. CENTRIFORCE provides resistance based on speed and acceleration, which allows it to feel hard when you're pushing it, but as soon as you back off, the resistance drops far more dramatically than with mag or fluid, allowing for a smooth feel that's more like riding on a flat road.