I wouldn't encourage you to buy these particular jaws. The jaw sizes usually go as the OD with the jaws fully closed. The inside diameter is then reduced by the thickness of the jaws themselves. So fully closed the Nova 50 mm has a 50 mm OD and a 41 mm ID.They also have 75mm heavy bowl jaws.
The jaws on the 75 have been made extremely thick such that the closed ID is only 46 mm. Personally I can't see any reason for this jaw profile.
I would direct you to look at the 70 mm jaws first, then the 100 mm jaws.