A filter element comprising a filter media and an outer surface. The filter media is formed in a closed loop, the closed loop defining a hollow interior extending along a longitudinal axis between a first end of the filter media and a second end of the filter media. The outer surface surrounds a perimeter of the filter element and is defined by a substantially circular first portion and at least one second portion. The first portion is substantially circular at a selected height of the filter media, and the at least one second portion is depressed relative to a circle defined by the substantially circular first portion at the selected height.