This versatile aluminum dovetail base is designed to accept any finder scope bracket or EZ Finder reflex sight bracket. It's an ideal base for custom installation of a finder scope on telescopes not already equipped with a compatible base.Synta-style dovetail base for finders and finder brackets. Will work with most compatible bracket designs from Celestron, Orion, Synta, Vixen, etc. Not meant for SCT telescopes which need a wider screw hole spacing. Drilled (but not threaded) to accommodate screws up to 4mm in diameter. Center-to-center screw hole spacing on your telescope must be 18.6mm (0.76") in order for this dovetail base to be compatible. Fits tubes 3.25" and larger in tube diameter (not telescope aperture), as well as flat surfaces. The base is made of die-cast metal and features a large thumbscrew lock. The Dovetail Base for Finder Scopes features a large thumbscrew lock to secure the finder scope bracket in place. Thanks to the size of the knurled thumbscrews, you can easily attach and detach your finder device, even when wearing heavy gloves. The dovetail base makes it easy to install a finder scope, or an additional finder, to any diameter refractor, reflector, Dobsonian reflector and Maksutov-Cassegrain telescope tubes. Includes mounting hardware.