a container assembly comprising a container of plastic material adapted for receiving a liquid and including a bottom of convex shape in the central portion of which the material is highly oriented . a stabilizing foot supports the container and for this purpose is welded to the container in the central portion of the bottom thereof whereat the material is highly oriented . the foot includes an annular projection extending downwardly from the portion welded to the container . the projection is hollow and forms an annular support foot including a rim which extends upwardly from the projection into smooth peripheral sliding engagement with the bottom of the container . the support foot is welded to the container while the middle portion of the projection is held against the middle portion of the bottom of the container .