Features: Due to its ability to produce exceptionally for sharp and clear images;this UHC filter is considered one of the most popular astronomy accessories;it can be used not only for celestial observations but also for astrophotography. 1.25'' barrel diameter simply attach to eyepiece cased in a sturdy transparent for case;standard filter thread for 1.25" eyepieces and other accessories. for Sky background is darker;and contrast of emission nebulae are noticeably improved;the perfect filter for viewing nebula from light polluted skies;or for boosting the contrast of nebula from dark for sky sites. UHC filters or light pollution reduction filters are designed to selectively reduce the transmission of certain wavelengths of light;especially those produced by artificial light. Optical glass lens;aluminum frame;significantly reduces light pollution;great for city and suburban observation. Specifications: Material: Glass+Metal Size: standard 1.25 inch Diameter: 4cm/1.57 in Note: Please allow 1-3cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 1x UHC Filter