We currently offer OE, ITG, and Green Filter brand air filters.
Paper or OE style filters filter elements the best but also block more air flow. Performance air filters use materials like cotton or foam to increase the air flow, but still offer significant air filtration.
Foam filters (like ITG) will flow slightly more than a cotton style filter, and excel at allowing more air even under dirty conditions. Cotton filters are more durable, but do require more maintenance to keep their elements clean to keep air flow clear.
Below is an example from Green Filter of air flow between paper, cotton gauze (like K&N) vs Green Filter brand woven cotton.