A hydraulic damper (1) is disclosed having the main damper tube (3) with a narrowed section (34) and including at least one additional piston assembly (8) adapted to be received in the narrowed section (34) to generate additional damping force. The piston assembly (8) comprises a compression valve assembly (82) and a rebound valve assembly (83) each comprising at least one deflective disc (823, 824). A sealing ring assembly (84) is disposed between the compression and rebound valve assembles and comprises a first annular member (841) having a plurality of channels (8411) covered by the deflective disc of the compression valve assembly; a second annular member (842) having a plurality of channels (8421), covered by the deflective disc of the rebound valve assembly; an axial projection (847) between the annular members radially internal to the axial channels; and a sealing ring (843a) displaceable axially between the annular members and radially over the axial projection and adapted to cooperate with the narrowed section (34) of the tube (3).