A piston configured to be used in a direct injection compression ignition internal combustion engine having a cylinder bore of about 175mm, the piston comprising: a piston body defining a longitudinal axis extending between a first axial body end and a second axial body end, and including an outer body surface extending between the first and second axial body ends (24, 26), and a combustion face upon the first axial body end; the combustion face forming a combustion bowl and including a conical inner bowl surface, and a concave outer bowl surface extending from the inner bowl surface to a cylindrical wall surface and having a compound curvature increased in sharpness in a radially outward direction; the combustion face further forming an annular piston rim extending circumferentially around the combustion bowl, and including a planar rim surface, and a convex lip surface transitioning between the rim surface and the wall surface and having an intersection with the wall surface that defines a boundary of the combustion bowl; and the outer bowl surface defining a large radius of curvature adjacent the inner bowl surface, and a medium radius of curvature adjacent the wall surface, and the lip surface defining a small radius of curvature, each in a longitudinal section plane, and the inner bowl, outer bowl, and wall surfaces (34, 36, 38) together contouring the combustion bowl, wherein the outer bowl surface has a bottom section adjoining the inner bowl surface and defining the large radius of curvature, and a transition section extending from the bottom section to the wall surface and defining the medium radius of curvature; and characterised in that a diameter of the combustion bowl is about 124 mm and a volume of the combustion bowl is about 190 cm 3, the large radius of curvature is about twice the medium radius of curvature, and the medium radius of curvature is about five times the small radius of curvature; and the planar rim surface defines a plane, and the bottom section of the combustion bowl is at a depth from the plane greater than the medium radius of curvature and less than the large radius of curvature. a piston body defining a longitudinal axis extending between a first axial body end and a second axial body end, and including an outer body surface extending between the first and second axial body ends (24, 26), and a combustion face upon the first axial body end; the combustion face forming a combustion bowl and including a conical inner bowl surface, and a concave outer bowl surface extending from the inner bowl surface to a cylindrical wall surface and having a compound curvature increased in sharpness in a radially outward direction; the combustion face further forming an annular piston rim extending circumferentially around the combustion bowl, and including a planar rim surface, and a convex lip surface transitioning between the rim surface and the wall surface and having an intersection with the wall surface that defines a boundary of the combustion bowl; and the outer bowl surface defining a large radius of curvature adjacent the inner bowl surface, and a medium radius of curvature adjacent the wall surface, and the lip surface defining a small radius of curvature, each in a longitudinal section plane, and the inner bowl, outer bowl, and wall surfaces (34, 36, 38) together contouring the combustion bowl, wherein the outer bowl surface has a bottom section adjoining the inner bowl surface and defining the large radius of curvature, and a transition section extending from the bottom section to the wall surface and defining the medium radius of curvature; and characterised in that a diameter of the combustion bowl is about 124 mm and a volume of the combustion bowl is about 190 cm 3, the large radius of curvature is about twice the medium radius of curvature, and the medium radius of curvature is about five times the small radius of curvature; and the planar rim surface defines a plane, and the bottom section of the combustion bowl is at a depth from the plane greater than the medium radius of curvature and less than the large radius of curvature.