While made for reading details on nautical charts this acrylic chart magnifier is endlessly useful in the home or office. No focusing is necessary. Simply look through it from a wide range of angles and distances - no squinting. With 6x magnification, the 'bright field' optical design has the effect of collecting light from all around and directing it onto the surface. It also makes an attractive chart or paperweight. The authentic compass rose (degree markings) inscribed on the bottom, makes it perfect for use with nautical charts. Made of flawless crystal-clear acrylic it delivers a 50% increase in magnification over its smaller kin, the #515 Crystal Magnifier.