I have a set of Kreitler Rollers with the killer head unit(fan) and it is a great work out. Much smoother than my old mag trainer. With the fan unit, you adjust the size of the air inlet to increase or decrease the resistance. There are also 3 pulleys that also change the fan speed. In addition the fan blows cooling air directly back onto your face as an added bonus. I have the fork mount for the days I do not want to worry about balancing on it or the wife wants to spin.