The flux is a compact and realistic interactive direct drive and is maintenance free the swift response of the smart electronics and the 7kg flywheel transmits the slightest fluctuations in resistance directly and accurately to your legs of all the tacx trainers the flux has the heaviest actual flywheel with an effect of 23kg the greater the flywheel effect the more realistic the cycling experience it uses ant and bluetooth smart for communication and can therefore be connected wirelessl