Firstly the base material, cotton, is the best material for vehicle air filtration. Its properties are perfect: it is organic so humidity and moisture will not affect it. When damp it dries quickly and thoroughly and is unaffected by different weather conditions and temperature. The harsh environment in the engine bay will not affect its performance. The green colour enables you to see the dirt being trapped by the filter so when heavy deposits build up you simply clean it.(Cleaning Guide) Foam Filters (sponges) and paper filters tend to absorb moisture and dirt rather than hold it. When wet, their filtration capability is limited. Cotton filters are produced from a renewable resource and are washable, reusable and create less waste than paper and foam filters, therefore being better for the environment.

The Green Advantage.
Save money, your car and the environment

Save Money
Cleaner air means cleaner burning fuel. This represents a 7% to 15% reduction in fuel use.
You can expect a Green Cotton filter to last the life time of the car so you can save money
on disposable paper filters.

Reduced Emissions and Waste
Cleaner burning fuel means less emissions from your car. No longer do you have to throw out your
disposable filter which will end up in landfill. Most factory filters are made of paper so you can also save trees.

Q. Do I sacrifice filtration for performance?
A. No, Green filters down to about 5 micron. Usually 60% of engine wear is caused by particles between 10 and 20 microns.
These filters have been developed in the extreme dirt, dust and moisture of rally and road tracks with maximum filtration in mind. The combination of the mesh and filter oil also result in a static charge to trap even smaller particles.
Q. Why choose a Green Cotton filter over a cheaper filter?
A. Some filter are cheaper than Green cotton filters but like everything a cheaper price usually means
a cheaper built product. Would you trust a cheap Chinese made filter to protect your engine?

Interested about what other people have to say about Green Filters? Check out this great review at here thanks to the guys from http://www.corvetteactioncenter.com. A great Corvette site with lots of good information.