Green red yellow blue... eight color filters fit for different bright objects;choose the filter which is the color the object you're viewing is not; such as moon, jupiter, Mars etc This filter allow you view bright objects which are so intensely bright it's very difficult to see it through a telescope without filter;You can really see the details Fits all standard 1.25Inch telescopes eyepiece and t adapter;thread inside tube Lens material;optical glass lens;provide clear image