The 10.75" Full Aperture Glass Solar Filter from Spectrum has been designed to fit telescopes with an OD range of 264mm to 270mm, and operates as a white light filter. This filter is a full aperture design, which means that it is designed to let you make full and complete use of the aperture of the telescope it has been attached to. It is suitable for any scope with an aperture between 264mm and 270mm. This translates to a range of 10.4" to 10.6" for optimal use.