The SVBONY 1.25" SII Filters are made of glass import from Germany that has been multi-coated with an ion-assisted deposition technology to ensure scratch resistance and stability on the central wavelength or CWL.
1. The Sulfur II 7nm Extra Narrowband Filter transmits a 7nm bandwidth of light that is centered at 672nm and drastically reduces other transmissions, including wavelengths of light that are responsible for light pollution (both artificial and natural). Like all SVBONY filters that are designated as “CCD”, this SII filter also blocks infrared wavelengths from 300nm to 1000nm so you don't need a separate IR-Cut filter
2. Thin metal cells have a clear aperture of 26mm for 1.25inch filters, each filter comes with a plastic case with high-pressure EVA case lining