From the Lumicon site:
"The Lumicon Enhanced Aluminum Diagonal reflects 96 to 97 percent of the light from the telescope's primary optics directly into your eyepiece. Its single 1/8 wave precision-polished surface is superior to the three surfaces of prism diagonals."
The diagonal is optically clean and comes with both a brass and a black nylon set screw. Original caps included. Please note in the photo that the barrel has noticeable marks that span the full circumference of the barrel from use in a previously owned SCT. Please do not purchase this diagonal if this is a critical issue to you.
$55 shipped FedEx ground to CONUS. Money order, bank check, or PayPal accepted.