Waterproof & Fogproof Wide Angle 46x with 65mm Pentax Scopes 58x with 80mm Pentax Scopes 74x with 100mm Pentax Scopes 18mm Eye Relief 60 Apparent Field of View Overview: Pentax eyepieces are a near consensus choice amongst serious amateur and professional astronomers as the best that's out there, quite an accomplishment indeed given the fervent passion of the collective. The XF lineup are less costly options which were designed for the PF-65ED and PF-65EDA midsized class of spotting scopes and their somewhat shorter focal length of 390mm. They can be used with any Pentax spotting scope, as well as with other telescopes which accept the standardized 1.25 eyepieces. The XF eyepieces are meet the J.I.S. "Class 4" standard for waterproofing, described by the Japanese regulators as water splashed against the enclosure from any direction shall have no harmful effects". Helicoid-type eyecup with four detented click-stop positions Parfocal with the XF 12 eyepiece, requiring no focus readjustments when exchanging the two Accepts 1.25" filters for astronomical & terrestrial applications Pentax premium spotting scopes adhere to the American standard of 1.25 eyepiece thread diameter, facilitating the use of eyepieces from independent manufacturers. That also means, of course, that the wonderful Pentax eyepieces can be used in other telescopes and spotting scopes which accept 1.25 eyepieces. Specifications" MAGNIFICATION: 46x (with the PF-65ED) ANGLE OF VIEW: 1.3 (with the PF-65ED) FIELD OF VIEW: FT@1000YDS/M@1000M: 66 (22 m at 1000 m) (with the PF-65ED) EXIT PUPIL DIAMETER: 1.4mm (with the PF-65ED) EYE RELIEF: 18.0mm RELATIVE BRIGHTNESS: 2.0 (with the PF-65ED) TWILIGHT FACTOR: 54.6 (with the PF-65ED) WEATHERPROOFING: Water resistant DIMENSIONS: 1.7 x 3.3 (43 x 83mm) WxH WEIGHT: 150