The bottom of the mounting stalk has a V-shaped base that is 30mm wide at its widest point. This will let it fit into the finder mounting bracket provided with most of the refractor and reflector telescopes from the above manufacturers. It lets you replace the inexpensive plastic single red dot finders and small refractor-type finders with the more flexible illuminated multiple reticle patterns of the Astro-Tech #ATF finder.

The top of the mounting stalk has narrow V-shaped ridges that the #ATF finder body clamps onto in order to lock the finder in place.