Don't put a standard-issue diagonal into a high-quality refractor or Cassegrain telescope or you'll be losing 10% or more of the light collected by the scope's optics. Use an Orion Enhanced diagonal instead. Their lab-tested enhanced aluminum coatings reflect 97% of the inbound light to your eyepiece, for brighter images compared to standard diagonals. Beautifully machined and anodized aluminum housings feature machine-threaded baffles for high contrast and nonmarring compression ring collars for securing the eyepiece. Nosepiece barrels are threaded to accept filters. Endcaps included.