[Seisunix] Bandpass Filtering

Hello All I am trying to apply bandpass filtering but I don't understand how should I define the frequencies in my data *sufilter < xcor_output_20_sources_B1.su f=5,10,15,20 amps=0,1,1,0 | filter_data.su <http://filter_data.su/>* How can I choose right frequencies (f values) in filtering? Thank you Erdi