The large pore, pre-filter captures the bigger particles
The small pore, inner filter prevents any engine-wrecking grit from reaching the cylinder
Uni Filter Inc. has been a foam air filter manufacturer since 1971. They have developed into the largest maker of aftermarket foam air filters in the world. Also, they produce air filters for Harley Davidson, Honda, Polaris, Bombardier, Arctic Cat, and many other motorcycle and ATV manufacturers.