Eyepieces focal length;0.16" 4mm;offer high magnifications;look more closely and more detailed at the moons surface and other planet; for viewing the moon and planets Standard 1.25’’ 31.75mm fitting diameter;can be used in any astronomical telescope with a 1.25" focuser;for broad field lunar observations; medium sized star clusters;and a wide range of cloudy nebulas and deep sky targets Fully coated optics glass eyepieces for excellent image contrast and light transmission;give maximum detail and definition across the entire field of view;highly achromatic;planetary filters enhance details on Jupiter;Saturn;Mars and Venus 4mm lens only weighs 0.09lb; For lenses with the same refractive index; the 62 degree aspheric eyepiece is thinner and lighter than the spherical eyepiece;designed primarily for planetary observation;perfect for deep sky objects Wide angle; 4mm 62 degree aspheric eyepiece can get maximum detail and definition across the entire field of view; Anti-lost design; Eyepiece interface recess portion can prevent the loss;Applicable;watch the scenery;bright celestial observations; nebula and so on Barlow lens the value must have 5x barlow lens doubles the magnification of any 1.25 inch eyepiece;double the capacity of an existing set eyepieces at the cost of a single eyepiece Quality aluminum stock and black anodized body 3 element 2 group lenses with multi coated optics design make image more crisp and sharp Qulity and shorty aluminum stock and black anodized body for a convenient long term use 2 element one group broadband green film multi coated optical glass;the housing is blackened to maximize image contrast;both that gets high quality observation without additional chromatic