A horizontal form-fill-seal (HFFS) machine comprising: a lower frame; a plurality of sealer bars comprising a first side sealer bar, a second side sealer bar, a third side sealer bar, a fourth side sealer bar, a first bottom sealer bar and a second bottom sealer bar; a first station comprising the first side sealer bar and the second side sealer bar; a second station downstream from the first station and comprising the third side sealer bar and the fourth side sealer bar; a third station downstream from the second station, wherein each of the first, second and third stations comprises posts extending from the lower frame, and each of the posts has mounted thereon a corresponding sealer bar from the plurality of sealer bars; and characterised in that the third station comprises the first bottom sealer bar and the second bottom sealer bar, and in that the horizontal form-fill-seal (HFFS) machine further comprises a fastener that mounts either: the third side sealer bar on the corresponding post in the second station, whereby the fastener is designed to reversibly and selectively move between a first configuration in which a position of the third side sealer bar on the corresponding post is maintained and a second configuration in which the third side sealer bar is movable to adjust a vertical height of the third side sealer bar relative to the lower frame; or one of the bottom sealer bars on the corresponding post in the third and fourth stations, whereby the fastener s designed to reversibly and selectively move between a first configuration in which a position of said one of the bottom sealer bars on the corresponding post is maintained and a second configuration in which said one of the bottom sealer bars is movable to adjust a vertical height of said one of the bottom sealer bars relative to the lower frame. a lower frame; a plurality of sealer bars comprising a first side sealer bar, a second side sealer bar, a third side sealer bar, a fourth side sealer bar, a first bottom sealer bar and a second bottom sealer bar; a first station comprising the first side sealer bar and the second side sealer bar; a second station downstream from the first station and comprising the third side sealer bar and the fourth side sealer bar; a third station downstream from the second station, the third side sealer bar on the corresponding post in the second station, whereby the fastener is designed to reversibly and selectively move between a first configuration in which a position of the third side sealer bar on the corresponding post is maintained and a second configuration in which the third side sealer bar is movable to adjust a vertical height of the third side sealer bar relative to the lower frame; or one of the bottom sealer bars on the corresponding post in the third and fourth stations, whereby the fastener s designed to reversibly and selectively move between a first configuration in which a position of said one of the bottom sealer bars on the corresponding post is maintained and a second configuration in which said one of the bottom sealer bars is movable to adjust a vertical height of said one of the bottom sealer bars relative to the lower frame.