Coolable piston for internal combustion engine

A coolable piston includes an annular wall extending between a crown and a lower distal end. First and second shoulders are provided in the wall. The first shoulder extends between first and second inner diameters of the wall. The second shoulder extends between the second and a third inner diameter. A collar is provided on the lower distal end of the wall and flanged over to project radially inwardly. An annular rib depends from the crown, with an annular cavity provided between the rib and the wall. An annular channel is formed in the rib. A ring member at least partially closes the cavity. The ring member is supported against axial movement by an inner periphery of the ring member being received in the annular channel. A locking ring is disposed in the collar against the second shoulder and supports an outer periphery of the ring member against axial movement.