:start shape:

    library = egs_shape_collection

    :start shape:
        type = sphere
        midpoint = 0 0 -0.18
        radius = 0.025
    :stop shape:

    :start shape:
        type = sphere
        midpoint = 0 0 0.18
        radius = 0.025
    :stop shape:

    probabilities = 0.5 0.5   
   
   # probabilities = 1 1
:stop shape: