GSO's Moon filter is an economical yet high quality eyepiece filter for reducing the brightness of the Moon so greater detail can be observed on the lunar surface. Has 18% light transmission. Green tint helps reduce glare and improve contrast. Has a standard 1.25" filter thread (M28.5x0.6) so it can be screwed on to virtually any astronomy eyepiece or accessory that has 1.25" filter threads. Comes in a protective plastic storage box. Made in Taiwan.