Thats what I thought but I did some research on K&N and apparently they were FIRST used back in the late 60s by desert offroad racers and became so popular because they outfiltered the paper filters of the era. I also just read that K&N has won more Baja-Style desert road races than all other filters combined. So I would assume that desert style racing would allow the most dirt to enter the motor but apparently the K&N filters worked better in these conditions according to the readings I just read.