Features: Substrates: precise polish substrates, good parallelism and surfaces precise Double-sided fine polishing and polishing process ensures high parallelism Coating: double-sided multi-layer coating, the backside increases the penetration film and reduces the reflect light High contrast filter (UHC filter) is choice of harmful light filter, it is more perfect Significantly reduce light pollution, suitable for city and suburban observation This 1.25inch UHC telescope filter is designed to improve the picture contrast of the subject. Diameter: 1.25 " simply attached to the eyepiece, installed in a solid shells Specifications: Material: Optical Glass Lens, Aluminum Frame Shape: Round UHC Filter Size:Approx.28.5x0.6mm/1.12x0.02in Thread: 28.5x0.6mm Glass Thickness:1.85mm Type: High Contrast Filter (UHC Filter) Package Includes: 1xUHC Filter note: Please allow 1-2cm errors due to manual measurement,please make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item.