Uni Filter Inc. has been manufacturing foam air filters since 1971.  They feature seamless polyurethane foam as the filtration media.  They have high air flow and superior filtration abilities, making them the choice for many motorcycle, dirt bike and ATV riders.

The principle of foam air filters is simple:  "Open Cell" Polyurethane foam is wetted with specially developed filter oil.  The "sticky" filter oil is suspended in the path of the dirty air strands of the web-like cell structure of the foam.  Dirt cannot pass through the depth of the filter without sticking to the strands.  As the outer strands become loaded with dirt particles, the wetted strands down stream start trapping dirt, allowing the entire thickness of the filter to be utilized.  This prevents surface loading or air restriction for 80% of the service life of the air filter element.  When the filter is sufficiently dirty, it is easily washed, re-oiled, and re-used.