Celestron Eyepiece Filter Set 1-1/4 (12,25,56,ND-25) Invaluable aid in lunar and planetary observing Reduce glare and light scattering All eyepiece filters are threaded to fit most1-1/4 inch eyepieces; filters offer a full 26 millimeter clear aperture Double-threaded, so they can be stacked (piggybacked) in various combinations Increase definition and resolution