This high quality transmits only 20%. It reduces glare and allows the user to relax the eye seeing more detail. It will also and most noticeably reduce the loss of night vision. Some moon filters are made using a plastic cell that can quickly become damaged in use. This unit has a precision machined anodized aluminum cell with an accurate neutral density filter that cuts down on the glare and brightness of our brightest celestial neighbor. With it's standard 1.25" filter thread (M28.5x0.6), it can screw into any 1.25" eyepiece. Comes in a plastic case.