In the sixth one from the line our new tutorial reviews, directed to serve students, university teachers and researchers, the dependence of the electron velocity on the drain voltage in ballistic MOSFETs, as well as its dependence on the gate voltage and on the inversion charge, are considered. At first glance, it seems unusual that in the ballistic MOSFET the speed is saturated with the increase in the drain voltage in the absence of electron scattering, however, the physics of this phenomenon is now quite understandable. In ballistic MOSFET, the electron velocity is saturated not at the drain end of the conduction channel, as in massive transistors, where the electric field is the largest and the scattering intense, but where the source ends and the conduction channel begins, i.e, at the top of the barrier where the electric field is zero.The saturation of the velocity, also known as the ballistic injection rate, is also discussed. It is this speed that is the upper limit of the injection rate in real MOSFETs. If 2 /2 S D n N , then the ballistic injection rate is constant, however, for 2 / /2 S D n N > this speed increases with increasing surface density of electrons. Simple calculations of the ballistic injection rate have been made, which can serve as a starting point for more thorough calculations. It is shown how the ballistic model and the virtual source model are interrelated. By simply replacing the traditional mobility, which is limited by scattering, in the virtual source model by ballistic mobility, we obtain the correct course of the ballistic linear current. By replacing the saturation velocity sat v in the massive conduction channel by the ballistic injection rate ball inj v , we obtain the correct value of the ballistic current ON I . It is also shown that the ballistic model predicts larger currents than the experimental data. This is due to the effects of electron scattering, understanding of which is extremely important for modeling nanotransistors.