These are some rings I have acquired over the years from various scopes I have had.
Vixen 80mm rings which are used for the 80mm refractor on the Vixen Alt/az mount. $25ppd
Celestron 142mm ID rings as supplied with the 6" refractor. $40ppd
Old Criterian 4 1/8th ID tube rings which I had modified to use with a 80mm guide scope.Can be used as guidescope rings or the guide scope screws can be removed to hold a OTA. Flat base has a recessed hole for mounting screw. $40ppd All sold/sale pending