CYG48B(CYG48P) vs CYG48G(RDL)
The CYG48G's hub is threaded and taper. So the hub of CYG48G is thicker than CYG48B’s hub.
The gear column of CYG-G has a device that holds the gap in five layers inside.
So it gives the astrophotographer confidence.
CYG48B can be upgraded to CYG48P, but not to CYG48G.