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. Finish may be smooth black or hammertone gray, depending on available stock. Style of large silver locking thumbscrew may vary.