With a wide 43-deg apparent field, Orions 40mm Sirius plossl telescope eyepiece provides clear, sharp images of impressively high contrast. Its suitable for all telescope types: reflector, Refractor, and catadioptric. Each 4-element Sirius plossl eyepiece is multi-coated for excellent light transmission. Lens edges are blackened to reduce scattering of stray light and maximize contrast. Lenses are mounted in Black anodized aluminum housings with 1.25" chrome-plated brass barrels. Each eyepiece is fitted with rubber eye guards and internally threaded to accept standard filters.