A planetary filter in a metal frame of 1.25 inches. Color # 29, i.e. dark red. It can be attached to any 1.25 "eyepiece with a filter thread and has a thread on both sides of the mount (the filters can be combined into color combinations).
Read our guide on filters and their applications HERE
Connection of ALL astronomical filters with the exception of solar film filters (which are filters for the lens) is accomplished by screwing the filter into the frame of the eyepiece from the opposite side than applying the eye (ie from the side that we put in the eyepiece extractor) . The filters can be additionally connected with each other, because they have threads on both sides of the luminaire.