Abstract: Plain cigarettes of unit length are fed into successive axially parallel peripheral flutes of a rotary drum-shaped first conveyor in such a way that each cigarette enters a first end portion of the respective flute. The second end portions of the flutes have suction ports which attract the cigarettes in alternate flutes so that such cigarettes move axially and provide room for introduction of additional cigarettes whereby each second flute contains a pair of coaxial cigarettes which define a gap for a filter rod section of double unit length. Pairs of coaxial cigarettes in alternate flutes are released for transfer into the axially parallel peripheral flutes of a second drum-shaped conveyor by a system of valving elements composed of a stationary valving element in the interior of the first conveyor and a rotary valving element which connects at intervals two axially parallel bores of the stationary valving element with a suction generating device.