A seat post assembly for a vehicle, comprising: an outer tube ; an inner tube telescopically movable relative to the outer tube ; a first locking member interposed between the outer and inner tubes to lock the outer tube to the inner tube at a first relative position between the tubes and at a second relative position between the tubes; and an actuator operatively connected to the first locking member where a first position of the actuator corresponds to a locked condition between the tubes and a second position of the actuator corresponds to an unlocked condition between the tubes ; wherein the first locking member comprises a first plurality of ball members and a second plurality of ball members symmetrically disposed about the second tube, wherein the first plurality of ball members are operable to lock the outer tube to the inner tube at both the first and second relative locations, and wherein the second plurality of ball members are operable to lock the outer tube to the inner tube at the second relative location; a first sleeve coupled to the actuator and having a large diameter portion for securing the first locking member into engagement with the outer tube by urging the first plurality of ball members and second plurality of ball members into ball lock recesses axially spaced along the outer tube at the first and second relative locations; characterized in that the second plurality of ball members move within axial slots disposed within the outer tube from the first relative location to the second relative location at which the second plurality of ball members abut ends of the axial slots to stop the axial movement of the inner tube relative to the outer tube . an outer tube ; an inner tube telescopically movable relative to the outer tube ; a first locking member interposed between the outer and inner tubes to lock the outer tube to the inner tube at a first relative position between the tubes and at a second relative position between the tubes; and an actuator operatively connected to the first locking member where a first position of the actuator corresponds to a locked condition between the tubes and a second position of the actuator corresponds to an unlocked condition between the tubes ; wherein the first locking member comprises a first plurality of ball members and a second plurality of ball members symmetrically disposed about the second tube, wherein the first plurality of ball members are operable to lock the outer tube to the inner tube at both the first and second relative locations, and wherein the second plurality of ball members are operable to lock the outer tube to the inner tube at the second relative location; a first sleeve coupled to the actuator and having a large diameter portion for securing the first locking member into engagement with the outer tube by urging the first plurality of ball members and second plurality of ball members into ball lock recesses axially spaced along the outer tube at the first and second relative locations; characterized in that the second plurality of ball members move within axial slots disposed within the outer tube from the first relative location to the second relative location at which the second plurality of ball members abut ends of the axial slots to stop the axial movement of the inner tube relative to the outer tube . <EOS>