This is the non-transparent overlay for the Intuos3 A6 Wide [PTZ-431] which, being a little rougher than the standard overlay, offers more resistance to the pen nib. Useful if you find the standard sheet too slippery.
An overlay is the thick plastic sheet that is placed on the active area of a tablet. It is simple to fix to the tablet with the double-sided tape at the top of the sheet. For use if the current sheet is damaged or you wish to use a different type of sheet.