I claim the ornamental design for a sheet for vehicle seats, as shown and described.
FIG. 1 is a surface view of a sheet for vehicle seats according to the design claimed;
FIG. 2 is a reference view of FIG. 1 showing the area of the detail; and,
FIG. 3 is an enlarged detail of area 3 circumscribed in the reference view, FIG. 2.
The broken line perimeter surrounding FIGS. 1 and 2 represents the boundaries of the claim and forms no part thereof. The broken lines circumscribing the detail in FIGS. 2 and 3 form no part of the claimed design. The design is flat and planar. The thickness and rear of the sheet for vehicle seats form no part of the claimed design.