A star wheel for a rotary packing machine, which includes a vertical shaft, a movable assembly with a frame fixed to said shaft, a plurality of pairs of arms, each arm is hinge mounted on the frame about an axis of rotation, an activation mechanism for each pair of arms, which activation mechanism moves the arms between an open position and a closed position, an adjustment mechanism, which moves the axis of rotation of each arm between two positions, and a locking mechanism, which locks the position of the axis of rotation, and a fixed cam.