An air filter assembly for an engine including a breather conduit and an intake conduit, comprising: a case comprising a first opening for receiving the breather conduit, a second opening for receiving the intake conduit, and a protrusion; and a filter element comprising: filter media having a closed loop, the filter media having a top and bottom; a first wall provided on the top of the filter media, the first wall having no openings; and a second wall provided on the bottom of the filter media, the second wall having a straight exterior side and a straight interior side with two separate apertures (170, 172) formed through the second wall from the straight exterior side to the straight interior side and a groove formed on the straight exterior side of the second wall, wherein the first and second apertures (170, 172) are equally sized and the same shape, and wherein the groove surrounds the first and second apertures (170, 172) and is configured to interface with the protrusion of the case; wherein the first and second apertures (172, 170) of the filter element are at least partially aligned with the first and second openings (180, 182) of the case, respectively; wherein the filter media, the first wall, and the second wall define an interior chamber of the filter element, and wherein the two apertures (170, 172) connect to the interior chamber such that air filtered by the filter media mixes with unfiltered gases from the breather conduit provided through a first of the two apertures by the first opening prior to exiting the interior chamber through a second of the two apertures into the second opening to the intake conduit. a case comprising a first opening for receiving the breather conduit, a second opening for receiving the intake conduit, and a protrusion; and a filter element comprising: filter media having a closed loop, the filter media having a top and bottom; a first wall provided on the top of the filter media, the first wall having no openings; and a second wall provided on the bottom of the filter media, the second wall having a straight exterior side and a straight interior side with two separate apertures (170, 172) formed through the second wall from the straight exterior side to the straight interior side and a groove formed on the straight exterior side of the second wall, wherein the first and second apertures (170, 172) are equally sized and the same shape, and wherein the groove surrounds the first and second apertures (170, 172) and is configured to interface with the protrusion of the case; filter media having a closed loop, the filter media having a top and bottom; a first wall provided on the top of the filter media, the first wall having no openings; and a second wall provided on the bottom of the filter media, the second wall having a straight exterior side and a straight interior side with two separate apertures (170, 172) formed through the second wall from the straight exterior side to the straight interior side and a groove formed on the straight exterior side of the second wall, wherein the first and second apertures (170, 172) are equally sized and the same shape, and wherein the groove surrounds the first and second apertures (170, 172) and is configured to interface with the protrusion of the case; wherein the first and second apertures (172, 170) of the filter element are at least partially aligned with the first and second openings (180, 182) of the case, respectively; wherein the filter media, the first wall, and the second wall define an interior chamber of the filter element, and wherein the two apertures (170, 172) connect to the interior chamber such that air filtered by the filter media mixes with unfiltered gases from the breather conduit provided through a first of the two apertures by the first opening prior to exiting the interior chamber through a second of the two apertures into the second opening to the intake conduit.