Composite filters are assembled initially by an upstream unit as groups of at least two plugs having different filtration properties. A single flow of the groups is directed from the assembling unit onto a pair of drums and divided into two flows, whereupon these are taken up by two pitch-adapting drums rotating substantially tangential one to another about parallel axes, and released to a rotating member turning on an axis normal to the axes of the drums and equipped with a plurality of carriers by which pairs of the groups are transferred from the drums to the twin channels of a garniture tongue along which two continuous rods of composite filters are formed. The carriers are equipped with an arm presenting a portion angled relative to the axis of the rotating member, so that two groups can be picked up at a time from the drums and deposited simultaneously in the channels.