"The original holes in the outer reinforcement were .280". During Testing, we found that if the holes were increased .030" (to approx. .310") air flow was increased greatly even when filter was partially obstructed with debris or moisture."
I'm sorry, but this is complete bs! They made the holes "approx. . 310" because that is a common size die (5/16" which is actually .312) They took the easy and cheaper way out.
