typical air filters are made out of paper and are highly restrictive with airflow
you'll never have to buy a new filter again all you gotta do is wash it and oil it every so often (once or twice a year)
better gas mileage, more power etc...
i've used these air filters for years on my Honda, WRX, RX-8 and now the new SHO, even got my family to use these filters in their Audi's
the hour i left the dealership with the new car off the lot I went to my local performance parts shop and had them overnight the part for me. the car had 800km's on it when i installed the filter
K&N gave some old guy who had a Pick up and drove it daily for work and personal use he reached the 1,000,000 mile warranty claim and K&N gave him a brand new truck
this video i made should explain the cleaning process
http://www.youtube.com/watch?v=yrzuGZF8Emk
plus on a cool note the car will make a loud turbo spool/woosh noise with this filter