This adapter is perfect for mounting cameras, weights or guide tubes to 3 "prism rails.
The lower part of the product image shows this application.
The stable rider terminal is built for heavy loads. The clamping is carried out not by a simple screw which presses on the rail, but on the entire surface. The length of the clip is 63 millimeters.
The terminal is compatible with all major prism rails: Losmandy, Farpoint, Baader, Celestron ...
About countersunk holes, you can attach with 1/4 "hexagon socket screws and M6 hexagon socket screws any accessories, such as cameras, barrel weights or Leitrohrschellen (the screws are not included).