90% transmission of the filters can block the light pollution of the city. Filter threads directly into the 2 inch barrel of your telescope eyepiece. 90% transmission means the filter also blocks the light from mercury and sodium vapour lamps. Standard M48x0.75 thread interface. The thickness of the filter can affect wavelength and dispersion of the filter. The filter can use with filter drawer and electronic camera. The Narrowband filter is designed for nebula observation. Package Includes:1x SVBNOY 2" OIII 5nm; 1x SVBNOY 2" H-Alpha 5nm; 1x SVBNOY 2" SII 5nm; 3x PP Material Plastic Box. SVBONY SV226 Holder for Filter Drawer Designed for SV226:This spare filter holder is designed for SVBONY SV226 filter drawers,It provides you with a more convenient combination. Can accommodate 2-inch round, mounted filters, along with other 2-inch round filters that measure 50.8 mm wide and 7.5 mm thick.