Recently, a new class of type I X-ray bursters was suggested, the ``burst-only sources'', i.e. detected only during an X-ray burst, and no persistent emission around the burst. Short follow-up observations of several burst-only sources could not unambiguously identify the X-ray burster, but suggested that they were at luminosities comparable to neutron star transients in quiescence. These sources are excellent candidates to study quiescent neutron stars, since the X-ray burst has unambiguously identified the compact object and they did not show an outburst in recent times. This will allow us to test several theories on the quiescent emission of neutron stars and open for the first time the possibility to study X-ray bursters at the lowest accretion regime.