This solar filter is for the new Galileoscope. It features an aluminum outer cell with a full aperture thin film displaying a natural yellow-orange image of the sun. The filter is secured to the telescope lens shade / dew cap with a nylon thumb screw. It is safe for solar viewing, blocking 99.999% sunlight. It is packed in a foam lined box and shipped in an outer shipping box. Specifications: The Outer Cell Inside Diameter is 3"(76mm) and the Clear Aperture Diameter is 2.37"(60mm). If you are interested in a solar filter that is the same size, with a glass aperture, type SF300 into the search box. You will be directed to this filter description.