4mm 62 degree wide angle aspheric eyepiece can get detail and definition across the entire field of view Standard 1.25''/31.75mm fitting diameter, can be used in most astronomical telescopes with a 1.25" focuser Optics glass eyepieces for excellent for image contrast and light transmission;give detail and definition across the entire field of view Offer high magnifications;look more and more detailed at the moon's surface and other planet; for viewing the moon and planets For lenses with the same refractive the 62 degree aspheric eyepiece is thinner and than the spherical eyepiece