what might not be good enough in all regions of the variables;

-   there is some inaccuracy in determining a particular shower age from the simulated shower, so that the derived electron distributions may refer to slightly different age than the chosen one;

-   even for the same primary characteristics of the shower the electron distributions may differ in different showers a bit above Poisson fluctuations due to some intrinsic fluctuations (see Section 4.4.3), although the exact universality would mean that they do not.

### Applicability to Auger showers

First, we shall check how well our universal fit describes the electron distributions in real (simulated) showers with primary energy $E_0=10^{17}$ eV at three ages $s=0.7$, $1$ and $1.3$. To do it we must build a sample playing a role of the registered showers to be compared with our fit. We shall not use now the same sample which served for the derivation of the universal fit; it contains smaller number of showers that we demand now, they are all vertical and do not correspond to those registered by Auger. Treating it rigorously we should simulate showers from the distributions of the primary energy $E_0$ and the zenith angle registered by 