15mm focus length.15mm is a intermediate eyepiece fit for observing the lunar surface planets binaries and bright nebula interior. 4 Lenses in 3 Groups: Multiple group lens combination to improve optical performance; the eyepieces delivers sharp images with good color correction and contrast. 16mm eye relief: Generous 16mm eye relief allows comfortable viewing distance and lets eyeglass wearers see the entire field of view. 6mm focal length; high magnification detailed observation; 6mm eyepiece can reveal intricate features such as surface detail on the Moon; cloud bands on Jupiter; or the rings of Saturn. 9mm focal length and 66 degree ultra wide angle provide an amazing magnification and broad vision,perfect for lunar observations,medium sized star clusters, especially for deep sky targets. 6 Lenses in 4 Groups:Multiple group lens combination to improve optical performance, and delivers sharp images with good color correction and contrast; --Blackened lens edges and internally blackened eyepiece barrel to avoid internal reflection and provide a crisp image.