Experimental results on the transmission of ultracold and cold neutrons through polyvinyl chloride tubes are presented. The dependence of the neutron transmission coefficient on the length and curvature of the tubes is studied. The possibilities of used tubes to create mobile and miniature sources of neutron and γ radiation as well as neutron-capture therapy are discussed.High transmission of ultracold neutrons by commercial polyvinyl chloride tubes was found in [1]. Polyvinyl chloride is a high-molecular chloride (CH 2 -CHCl) n with extremely high molecular mass 30000-100,000 amu, which is widely used in different fields of science and technology, including medicine, electronics and the food industry, is readily available and inexpensive. Polyvinyl chloride tubes are elastic, which makes it possible to use them to transport solutions and gases to locations which are difficult to access. The limiting velocity of polyvinyl chloride is not very high, equaling 2.9 m/sec. However, if a thin layer of a material possessing a higher limiting velocity but retaining specularity of the inner surface is deposited on the surface of polyvinyl chloride, then such tubes can be effectively used to transport low-energy neutrons in an arbitrary direction. The photopolymer Fomblin YL VAC 18/8 can be used for such a coating; it comprises a viscous liquid which when deposited on a surface a room temperature forms a smooth specular layer with limiting velocity 4.56 m/sec. The absorption coefficient for neutrons incident on such a layer does not exceed (2-3)·10 -5 . For such an absorption coefficient, a neutron undergoes ~10000 specular reflections from walls before absorption becomes noticeable. Figure 1 shows for 190 and 290 cm long tubes the change of the transmission coefficient of ultracold neutrons T = I/I 0 , where I 0 and I are the neutron fluxes at the exit of a straight tube and a tube curved in a definite configuration, respectively. A tube with inner diameter 8 mm, at whose inlet ultracold neutrons with velocity 3.2-6.2 m/sec were delivered, was used in the experiment.The present authors also measured the transmission of cold neutrons through such tubes (Fig. 2a). The cold-neutron source was a beryllium converter place on the bottom of an 8.8 cm in diameter, curved, mirror neutron guide. The converter was placed near the beryllium reflector of the core of the IR-8 reactor. The inner surface of the mirror neutron guide was coated with a layer of an alloy of 58 Ni and molybdenum with limiting velocity 7.9 m/sec. Neutrons with axial velocity from 6.9 to 180 m/sec with the average value 57 m/sec flowed from the outlet nozzle. The transverse velocity of the outflowing neutrons did not exceed 7.9 m/sec. Photopolymer coated tubes with diameter 8 mm and different lengths were connected to the outlet nozzle of the neutron guide, covered with a flat flange with an 8 mm in diameter opening through which the neutrons entered the tube. The remaining neutrons were absorbed in the flange. The neutron flux was measured with a gaseous propo...