Abstract: An air cylinder for supporting a moving web of material during heat treatment, particularly during drying, of such web. The cylinder comprises a plurality of nozzles which are arranged in a part-circular array around which the moving web passes, the nozzles being of the Coanda type wherein the discharge gaseous medium flows over a transversely extended lip surface of the nozzle between the extended surface and the adjacent surface of a web being treated and is caused to cling to such extended surface by the so-called Coanda effect.In order to support the moving web particularly stably in the radial direction relative to the cylinder, the nozzles are arranged in pairs, with the respective transversely extended surfaces of the two nozzles in each pair extending in opposite directions whereby air flowing over these two extended surfaces flows in opposite circumferential directions to respective radially inwardly directed air outlets.