I'm not sure what these were used for, or even if they were used in the comic production process (they came in a large collection I recently purchased).  They each measure approximately 8 1/2 by 10 1/2 inches and there are two 2-layer overlays (the text/logo layer and the artwork layer).  Placed together they form the full image.  In excellent condition, they will be shipped with the utmost care.