A good quality, solid, T-Adaptor.
The only problem, not related to any deficiency in the product itself, is that most reflector telescopes (including some Celestron models) won't be able to bring the focus-point of the telescope past the eyepiece socket (and, thus, into this adaptor) with even the best of cameras on their own. That's just simple physics, where the focus-point is actually inside the eyepiece socket tube and is only extended by eyepieces with lenses, or Barlow lenses. You'll know this is the case for your telescope if holding the camera on the empty eyepiece means you can't focus your camera enough to get a clean image.
Celestron sell an equivalent to this adaptor with a Barlow lens integrated which solves the problem, which is also available on Amazon.