Standard Synta-style dovetail base for finder brackets. The two holes perpendicular to the optical axis are drilled to accept M4 machine screws. The two holes along the optical axis are drilled to accept M5 machine screws (and can accept M4 screws as well).
The base is made of die-cast metal and features a large thumbscrew lock. Center-to-center screw hole spacing to use the holes on your telescope must be 18.6mm (0.76") in order for this dovetail base to be compatible (perpendicular to the optical axis). Fits tubes 3.25" and larger in tube diameter (not telescope aperture), as well as flat surfaces.
Please see the photos above for detailed dimensions and to determine compatibility with your telescope or finder/finder bracket - we are unable to make specific recommendations about compatibility. Please also note that the hole spacing for the two additional screws along the optical axis (one of which is used for attaching this base to a focuser) is not fixed. Since only one screw hole is to be used at a time, this is not an issue.
Finish may be smooth black or hammertone gray, depending on available stock. Style of large silver locking thumbscrew may vary.