The Tele Vue DET-0416 attaches on one side to a Tele Vue eyepiece barrel via non-marring set screws, and the other side accepts your camera's specific T-mount adapter-allowing you to digiscope with your Tele Vue eyepiece and SLR together.
Not every Tele Vue eyepiece works with the DET-0416; specifically due to the nature of digiscoping work, Tele Vue only recommends the 32mm and 40mm Plössls, 27mm and 35mm Panoptics, 12m, 17mm, and 22mm Nagler type 4s, and 31mm Nagler type 5.