Pentax SMC XW Spotting Scopes Eyepieces 23.0 mm 85 Angle Black. The high-performance optical design includes lanthanum glass elements with high refractive power and low dispersion to deliver a balanced image with minimal aberrations. The design effectively compensates for spherical aberration of the pupil so is specially good at reducing the annoying 'blackout' effect. Specifications for Pentax SMC XW Spotting Scopes Eyepieces: Manufacturer: Pentax Finish: Multi-Layer Field of View Angle: 85 degrees Diameter: 76 mm Eye Relief: 20 - 12 mm Weather Resistance: Yes Package Contents: Pentax SMC XW Spotting Scopes Eyepieces Pentax 70541: SMC XW Spotting Scopes Eyepieces 23.0 mm 85 Angle Black