This is the standard dovetail shoe that comes on the Stellarvue FSV25B focuser.
Please note: This shoe is not designed for the old dovetail rail that is narrower and was once supplied with Stellarvue rings. This discontinued rail is shown to the left. The new TPFD rail is much wider. If you want to use this shoe with your older rings you must also replace the old, narrow rail with the TPFD rail.