LoudMouthMX is a unique company, with a different product. If you are not familiar with the LoudMouth Air Filter system, simply put it is WAY easier to change the air filter and provides more airflow to the motor (more Air = More Power). The way it achieves better air flow is very simple, there is more space around the filter for the motor to draw air from. The picture is a CRF450 with the Loudmouth installed, as you can see there is plenty of space around the filter. If you have or ever have had a CRF450 or CRF250 than you know putting the air filter in is like stuffing 10 pounds of crap in a 5 pound bag. I definitely would recommend buying one of the LoundMouthMX systems. They also make some other parts and have a lot in development for MotoCross...    

Click on their logo at the top of the page to go to their website.