The ornamental design for a lid for containers, as shown and described.
FIG. 1 is a perspective view of a lid for containers according to my new design;
FIG. 2 is another perspective view of the lid for containers according to my new design;
FIG. 3 is another perspective view of the lid for containers according to my new design;
FIG. 4 is a top plan view of the lid for containers according to my new design;
FIG. 5 is a front elevational view of the lid for containers according to my new design, the rear, right and left elevational views being the same; and,
FIG. 6 is a bottom plan view of the lid for containers according to my new design.