An extraction unit (10) for extracting cartridges (1a;1b) of two different dimensions (da,ha;db,hb) comprises a seat (14,20) for receiving any of such cartridges (1a;1b) and for extraction thereof in the seat. The unit (10) further comprises a pair of slides (19a) for guiding any of such cartridges (1a;1b) towards the seat (14,20) in a sliding contact of each of these slides (19a) with a cartridge guide (5a;5b) of the cartridges (1a; 1b). The slides are relatively movable to be spaced selectively by a first and second distance (Da, Db) according to the size (da, db) of the cartridge.