This is a great value-for-money mirror star diagonal which allows you to look through the eyepiece from a comfortable sitting-down position, rather than crouching down to try and look through the instrument. Also great as a second diagonal if your own is lost or damaged. Don't be put off by the plain-looking plastic body and nose-piece — the mirror they encase is much, much better than others in the same price range (like those you typically get bundled in with entry-level telescopes)