The QHY-OAG-L Off-Axis Guider is for large-sensor cameras such as the QHY(IC)16803 and other matching accessories like the QHYCFW2-L filter wheel. The body and pick-off prism size is the same as for all QHY Off-Axis Guiders. It is just the telescope/camera interface which is sized to accept thread adapters of different diameters. Whatever the diameter of the interface, there are six 3 mm holes and the same thickness of 10 mm (without adapters installed.) Both the telescope side and camera side adapters have a thickness of 3 mm. The final thickness of the OAG depends on whether you need to use just the telescope side thread adapter or both adapters. If you are using the QHYCFW2-L, for instance, it will connect directly to the OAG-L, and you won't need to use the camera side adapter.
The QHY-OAG-L has a diameter of 68 mm and will accept M42 x 0.75, M54 x 0.75, and M60 x 0.75 adapters. It will work with cameras that have larger sensors, such as 37mm x 37mm, 36.24mm square or 48mm x 36mm (although the 50100, which has a 48mm x 36mm sensor, would require a special adapter, which is not included in this package.)
All QHY-OAG models have an 8mm x 8mm multi-coated pick-off prism. Its position can be adjusted as desired and then locked into position with a thumbscrew. It also comes with a locking, multi-thread 1.25-inch focuser having a focusing range of about 6 mm (1/4"). If you use the QHY5L-II--or others having a similar form factor--as your guide camera, its position is adjustable when inserted into the QHY-OAG. These two adjustments will give you a wide range of focus accommodation.
Please Note: Choose the Medium version of the OAG if you want to use a camera with an APS-C, APS-H or 36x24 sensor, such as the QHY(IC)16200A, or you have the QHYCFW2-M filter wheel.