Compatiblity; Standard 1.25inch eyepiece barrel can fit any telescope with 1.25in interface; M28.5x 0.6 filter thread for 1.25inch filter; 40mmfocal length perfect for observing the moon and the Milky Way Good optical; 4 element in 2 groups high quality optical lenses with FMC film design increases light transmission and provides bright clear image Crisp image; blackened fully threaded barrel design to avoid internal reflection and provide a crisp image; lens edges is blackened to reduce scattering of stray light and maximize contrast Comfortable; foldable rubber eyecups is comfortable for people with or without eyeglasses; 40 degree apparent field of view eyepiece acquiring and centering target objects a breeze Portable and durable; fully metal design is sturdy and solid for using a long time; comes with a plastic case is easy to carry and store