We stock the IOR scope rings in "low", "medium" and "high" format. They are of a solid, steel construction
There seems to be no defined measurement for these formats, but it would seem that "low" format rings will do for all scopes having objective lens diameters up to 50mm. For bigger object lenses, "medium" or "high" format rings are required.
However, it is almost impossible to guarantee that the two scope rings will be perfectly aligned, so we recommend that you also purchase a lapping kit to lap your scope rings in and prevent damage to your scope due to mis-aligned rings.