The Optolong H-alpha 7nm filters allow 7nm bandwidth of light centered on a wavelength of 656nm through, reducing the transmission of certain wavelengths of light, specifically those produced by artificial light including mercury vapor, and both high and low pressure sodium vapor lights and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. skyglow).
WARNING: The filters of Optolong are not designed for sun observation. DO NOT LOOK AT THE SUN WITH OPTOLONG FILTERS. You would be BLIND if you fail to observe the warning.