Ricoh Pentax XW40-R 40mm Extra Wide Eyepiece w/ 2in Barrel, Black, Medium, 70538. Provides exceptional performance with fully multi-coated lenses and extra-low dispersion lanthanum glass to deliver high-contrast full-field images. The light-shielding asymmetrical multi-layer coatings ensure the transmission of light and significantly reduce internal reflections. Exposed rheostat enables the Light Shielding Dilaphragm to block stray light from the front lens elements and significantly increase light transmission. This is why the Ricoh Pentax XW Telescope Eyepiece is an advanced light-weight eyepiece for astrophotography with a twist-up eye cup. The only drawback of this advanced eyepiece is that it requires two eyepieces to accomodate a variety of filters and may not work with binoculars. However it is an excellent benefit for spotting wildlife or for terrestrial use. With a larger exit pupil and twist-up eye cup feature the Ricoh Pentax Telescope XW Eyepiece offers improved performance over older models. Specifications for Ricoh Pentax XW Eyepiece: Manufacturer: Ricoh Color: Black Field of View Angle: 70 degrees Eye Relief: 20 mm Features of Ricoh Pentax XW Eyepiece 2in barrel Weatherproof Eyepiece (not submersible) Extra-Low-Dispersion Lanthanum Glass Phase Coating on all surfaces Light Shielding Diaphragm to Drastically Reduce Internal Reflections Adjustable twist-up eye cup Available in 3.5mm 5mm 7mm 10mm 14mm 20mm 30mm and 40mm focal lengths Package Contents: Ricoh Pentax XW Eyepiece Caps Plastic Case Ricoh 70538: Pentax XW40-R 40mm Extra Wide Eyepiece w/ 2in Barrel Black Medium.