US Patent 7282077 Air cleaner assembly

An air cleaner that includes a first housing portion having a non-circular attachment fit. A second housing portion is attached to the first housing portion to define a filter space. A filter element includes a non-circular filter aperture that defines a perimeter that is completely defined by four equal arc length segments. The filter aperture is engageable with the attachment fit. The attachment fit and the filter aperture are sized to provide substantially equal contact pressure around the perimeter of the filter aperture when engaged with one another.