The Lumicon LD1005 2" Mirror 90° Diagonal features compression-ring eyepiece holders. With this mirror, light is reflected up into the eyepiece providing a clear, bright image. In this way, you'll hardly lose anything from what your telescope sees. It may also be used on refractors, and upon SCTs with an optional 2" visual back (which is included with many SCT scopes).
Compression ring eyepiece holder, instead of marring set screw
Accepts 48mm screw-in filters