Muzzle-Loaders.com now had Williams Ghost Rings in stock.
This sight will fit on any rear ramp, such as a Williams or Durasight that come factory on most muzzleloaders. We checked with all of the muzzleloaders that we currently stock, and the Ghost Ring will fit any Knight, Traditions, or Thompson Center inline rear sight on the market. This design is the same height as a standard iron sight, so you will not have to shim the rear sight for proper alignment.
Coming soon: Ghost Ring sight for CVA rear sights.
You can see the Williams Ghost Ring here:
http://muzzle-loaders.com/optics/sights/williams-ghost-ring-fiber-optic-sights.php