Abstract: A round baler is provided which comprises a bale chamber which is expandable between a bale start position and a full bale position and which comprises a first bale-forming means disposed generally circumferentially around a portion of the full size bale chamber when the baler is in its bale-forming condition, and a second bale-forming means which is movable relative to the first bale-forming means between two extreme positions. The second bale-forming means is cooperable, in one extreme position, with the first bale-forming means to form the bale start chamber of reduced dimensions for starting bale formation, and, in the other extreme position, with the first bale-forming means to define a generally cylindrical bale chamber generally corresponding to a full size bale. The first and second bale-forming means are cooperable to form a round bale of crop material during movement of the second bale-forming means from the one extreme position towards the other extreme position.