This product is attached to the table, providing a parallel mounting location for another object 5 mm away from the table end.
This adapter gives more flexibility to your optical mount. By aligning the front face of the optic to the center of the post, it prevents any deviation in the optical path of your assembly as it rotates.
This adapter also extends the field of application by attaching to the post, opening a slot at 5 mm from an object parallel to the post.