Celestron Wide Angle Eyepiece for Regal M2 Versatile eyepiece can be used on Celestron spotting scopes, telescopes and other optical instruments that have a 1.25" eyepiece mount Twist-up eyecup and 20mm eye relief provides a full field of view and comfortable viewing with or without eyeglasses Waterproof and nitrogen purged for use in all weather conditions -Nitrogen gas prevents internal fogging Celestron' s proprietary XLT coating increases light transmission through the optical path for brighter images and increased resolution Housing is filled with dry nitrogen gas to prevent the internal lenses from fogging