Made to mount Stellarvue 50 - 60 mm finder scopes to the Feather Touch 2.5” - 3.5” focusers. Will not mount to Feathertouch 2" focusers. The shoe mounts to these specific focusers, to any flat surface, or to a tube that is 4” or greater in diameter. When installing the shoe on the Feather Touch focuser obtain 8-32 screws of the proper length. Please be aware if the screws are too long they will scratch the focuser drawtube. So take the shoe with you to make sure the screws are not too long.