This is a saddle that will fit to D or V series dovetail bars, and upon which are installed by default a duo of 100mm guidescope rings.
The saddle may be adjusted freely to fit your saddle via turning knobs on the sides.
The 100mm rings are a great size for a wide variety of guidescopes and other similar devices of similar size. There are two rings.
The guidescope rings are also adjustable, the large delrin scews inside very suitable.