ES 2" DiagonalFeatures The Explore Scientific 2 inch Dielectric Coated Diagonal Mirror comes complete with 1. 25 inch Adapter and dust covers. Solid construction and light weight, this first suface coated diagonal mirror reflects 99% of the light to help maintain the brightest possible image from your telescope. The insert barrel is a double taper, so it can be smoothly inserted or withdrawn from the focuser. The wide part of the taper prevents the diagonal from