def SexoFP_(kin_RE,kout_RE,Vspine):
    """Returns the fixed point of the exocytosis event size Sexo, i.e. the number of AMPARs delivered to the spine membrane during one exocytosis event.

    Parameters
    ----------
    kin_RE : float
        Rate at which AMPAR containing endosomes enter the spine (dynamics of exocytosis event size Sexo).
    kout_RE : float
        Rate at which AMPAR containing endosomes leave the spine.
    Vspine : float
        Spine volume.

    Returns
    -------
    float
        Fixed point of the exocytosis event size Sexo.
    """
    
    return kin_RE/kout_RE*Vspine