An assembly for an extendable and retractable boom of an agricultural machine, comprising - a first boom section having a first frame structure comprising a plurality of frame elements; - a second boom section connected to the first boom section by an articulating joint configured to allow 180 degrees rotational movement between the first and second boom sections , thereby, relocating the first and second boom sections between an extended boom section arrangement and a retracted boom section arrangement; - an arrangement of hinged elements connected to both the first and the second boom sections ; and - an actuator mechanism, the actuator mechanism comprising an actuator received inside the first frame structure of the first boom section and functionally connected to the arrangement of hinged elements , wherein the actuator mechanism and the arrangement of hinged elements are configured to produce the 180 degrees rotational movement between the first and second boom sections , and the actuator is configured to drive the 180 degrees rotational movement; the assembly for an extendable and retractable boom being characterized in that the arrangement of hinged elements comprises - a plurality of link arms provided in a link arm arrangement, wherein a distal end of the link arm arrangement being distal to the actuator is connected to the second boom section and a proximal end of the link arm arrangement being proximal to the actuator is connected to the actuator ; - a first lever element , wherein the first lever element is pivotally connected on opposite sides to the actuator and a first mounting point , respectively, the first mounting point being located inside the first frame structure of the first boom section ; and - a second lever element , wherein the second lever element is pivotally connected on opposite sides to an articulating joint of the link arm arrangement and a second mounting point , respectively, the second mounting point located inside the first frame structure of the first boom section . - a first boom section having a first frame structure comprising a plurality of frame elements; - a second boom section connected to the first boom section by an articulating joint configured to allow 180 degrees rotational movement between the first and second boom sections , thereby, relocating the first and second boom sections between an extended boom section arrangement and a retracted boom section arrangement; - an arrangement of hinged elements connected to both the first and the second boom sections ; and - an actuator mechanism, the actuator mechanism comprising an actuator received inside the first frame structure of the first boom section and functionally connected to the arrangement of hinged elements , wherein the actuator mechanism and the arrangement of hinged elements are configured to produce the 180 degrees rotational movement between the first and second boom sections , and the actuator is configured to drive the 180 degrees rotational movement; - a plurality of link arms provided in a link arm arrangement, wherein a distal end of the link arm arrangement being distal to the actuator is connected to the second boom section and a proximal end of the link arm arrangement being proximal to the actuator is connected to the actuator ; - a first lever element , wherein the first lever element is pivotally connected on opposite sides to the actuator and a first mounting point , respectively, the first mounting point being located inside the first frame structure of the first boom section ; and - a second lever element , wherein the second lever element is pivotally connected on opposite sides to an articulating joint of the link arm arrangement and a second mounting point , respectively, the second mounting point located inside the first frame structure of the first boom section . <EOS>