A stopper/piston (510) having a cylindrical body (511) having a front axial end closed by a front wall (513). The hollow cylindrical body (511) includes an outside surface provided with a secondary sealing profile (610), the front wall (513) including a front axial outside surface (631) provided with a coating (635). The front wall (513) includes a primary sealing profile (630) on its radially-outer edge, the front wall (513) and the cylindrical body (511) is made of different materials, the hollow cylindrical body (511) being overmolded on the front wall (513). The front axial outside surface (631) of the front wall (513) includes a deformation profile (633) arranged radially inside the primary sealing profile (630), the deformation profile adapted to deform radially for insertion of the stopper/piston (510) into a syringe body.
