Micron Ratings and Open Area:
The document provides a table listing various micron ratings alongside their corresponding opening sizes in inches and the percentage of open area. The micron ratings range from 25 to 350, with opening sizes from 0.001 to 0.014 inches and open area percentages from 2.1% to 23.0%.

Open Area Percentage by Micron Rating:
Another table shows the percentage of open area for specific micron ratings: 75, 50, and 25, with open areas of 43%, 36%, and 33% respectively.

Nominal and Absolute Ratings:
The document also includes a comparison of nominal and absolute ratings for various micron levels. Nominal ratings range from 10µ to 150µ, while absolute ratings range from 10µ to 150µ, indicating the precision of filtration at different levels.