The use of smooth, hollow glass capillaries for neutron optics was discussed elsewhere (1,2,3). By means of such capillaries, neutron lenses were constructed, which allowed an increase of neutron flux at the focal point by a factor of 10–15. However, up to now the transmission of capillary systems was rather poor; for example, the flux enhancement for the neutron lenses should be at least two orders of magnitude more than observed. The same conclusion comes from direct measurements of the transmission of curved capillaries (3).