What is the difference between Super Screen 17x14, 17x20, and 20x20?

Super Screen 17x14 is standard and offers 3 times the durability of standard fiberglass mesh, without sacrificing visibility or airflow. 

Super Screen 17x20 offers the same durability + enhanced insect protection while maintaining good visibility and excellent airflow. 

Super Screen 20x20 offers superior durability and insect protection with minimal loss in visibility and airflow.