Composition of cosmic rays at ultra high energies

► Measurements of CR composition above 1015 eV by Yakutsk EASA are presented. ► Interpretation of these results in terms of CR mass composition is given. ► Mean logarithm of the CR atomic number has the peak value ∼2.5 achieved at ∼1017 eV. ► Then it substantialy decrease within the energy interval 1017 − 1018 eV to ∼1. ► This behavior indicate for the transition from galactic CR component to extragalactic at 1017 − 1018 eV.