Full size overlays can be preferable to the smaller, more convenient Reading Rulers in a number of cases. For example where factors of age or disability cause coordination problems, or when both hands are engaged while text and other representations are being followed (such as when reading music or following a recipe).
One side of the overlay has a matt coating. Some matt coatings can reduce the transparency of a tinted overlay, but overlays from Crossbow Education have been subjected to stringent testing to ensure that maximum print clarity is retained while reflected light from the overlay surface has been significantly reduced. Nevertheless, some people prefer using the gloss side of the overlay.