Yamaha Twin Air Air filter

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From everyday riding to the most extreme conditions you need the protection Twin air filter provide. They feature- 

A Coarse open pour outer foam matched with a fine open-pore inner foam acts as a second filter to trap the smallest particles while ensuring maximum air passage.

Exclusively formulated adhesive ensures glue seams will not break down.

Thick, flat foam, greaseless sealing ring ensures maximum contact with your airbox, while acting as a breathable gasket for increased air passage.

Fused outer and inner elements prevent dirt and grime from being lodged between layers, unlike Twin Air, this can be a problem with inferior two piece designs. Trapped particles can restrict airflow. And if dirt works its way into your engine, a pinhead sized granule could gouge your cylinder, piston and rings.

Most designs are smaller than stock filters to increase the airspace around the filter.