A quality super plossl eyepiece with full multi-layer coating. Can be used as a normal eyepiece or to use for eyepiece projection photography it has an external extendable sheath with a removable cap. This reveals a T2-thread (42mm) suitable for connecting to your camera's T- ring. Focal Length = 40mm Barrel Size = 1.25" Apparent FOV = 45° Eye Relief = 31mm Group: = 4-elements Filter Thread = M28.5 x 0.6 Camera Thread = M42 x 0.75