The beauty of this design is that it lies flat on the paper and you simply look through it. Endlessly useful in the home, office and shop. No focusing is necessary, and it can be comfortably viewed with both eyes from a wide range of angles and distances - no squinting. The 'bright field' optical design has the effect of collecting light from all around the loupe and directing it right onto the surface you are looking at. Also makes an attractive paperweight. Approx. 4" in diameter.