A bag (1) suitable for separably associating with a lawnmower (2) is described, comprising an inlet (3) provided with an edge (4) which has a lower edge (5) and two lateral edges (6), and a conveyor (7) of cut grass provided with a lower edge (8) rotatably associated with the lower edge (5) of the bag (1). The conveyor (7) comprises reversible hooking means (20) to at least one lateral edge (6) of the edge (4) of the inlet (3).