The invention relates to a piston rod (20) for an injection device comprising a first and a second legs (30 40) each leg being foldable on itself and comprising a proximal region said piston rod (20) being in one of a folded position and an unfolded position said piston rod (20) comprising coupling means (33 34 35 43 44 45) for coupling the proximal region (32) of the first leg to the proximal region (42) of the second leg when said piston rod (20) is in said unfolded position. The invention also relates to a kit comprising said piston rod.
