The ornamental design for a jar for cosmetics, as shown and described above.
FIG. 1 is a perspective view of our new design for a jar for cosmetics;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is an opposing side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines in the drawings showing the jar for cosmetics illustrate the portions of the jar for cosmetics that form no part of the claimed design.