The information I have is:
6 1/2" *condensers are used with 135mm and 150mm lenses for 4x5 negatives
4 11/16"condensers (this is the actual diameter of the glass, part of which is under the edge of the aluminum housing) are used for lenses 75mm-90mm for 645-6x6-6x7-6x9 negatives
3 1/2" condensers (this glass is also partially covered by the aluminum housing) are used with 50mm lens for 35mm negatives
The measurements are the diameter of the glass.