The filamentation instability between counter-propagating beams of electrons is important for the magnetic field generation in astrophysical jets. Here this instability is considered for equally dense counterpropagating electron beams. It is demonstrated that the plasma evolves into a state, in which the electric fields driven by the magnetic pressure gradient balance the magnetic forces. This system is stationary in the 1D PIC simulation. The size distribution of the current filaments closely follows a Gumbel distribution within the statistical limitations.