An air cleaner comprising a housing including a surrounding housing-wall defining an open interior; an inlet arrangement; and an outlet arrangement; the inlet arrangement and outlet arrangement being at opposite ends of the housing; the housing defining an access opening in communication with the open interior; a cover removably secured to the housing over the access opening; the cover having an exterior surface and an opposite interior surface, the interior surface facing the housing open interior; and a cassette-free filter cartridge removably oriented for selective removal within the open interior between the inlet arrangement and outlet arrangement; the filter cartridge including a media pack having opposite inlet and outlet flow faces; the media pack comprising a plurality of flutes extending in a direction between the inlet flow face and the outlet flow face; the media pack being closed to air entering the inlet flow face and passing outwardly from the outlet flow face without filtering flow through media of the media pack; and a seal member secured to the media pack; the seal member forming a releasable seal with a sealing surface in the housing so that the filter cartridge is in sealing engagement with the housing; the filter cartridge including a cartridge-handle; and wherein (a) the interior surface of the cover includes a receiver that contains at least a portion of the cartridge-handle when the filter cartridge is operably oriented within the housing interior and when the cover is secured over the access opening, (b) the filter cartridge includes a shell with first and second opposing shell walls (606, 607) secured to the media pack; the cartridge-handle projecting from the first shell wall; (c) the shell includes a frame extending between and joining the first and second shell walls; the frame being mounted against the second flow face of the media pack; the frame including: (i) a base member defining an airflow opening arrangement in communication with the second flow face; (ii) a seal support section extending from the base member along a perimeter of the airflow opening arrangement; (d) the seal member is oriented against the seal support section; (e) the cover further includes a projection arrangement extending from the interior surface into the housing open interior, when the cover is secured over the access opening; wherein: (f) the projection arrangement includes at least first and second legs (645, 646) extending from the interior surface of the cover; and (g) the receiver is between the first and second legs and laterally spaced therefrom; characterized in that: the projection arrangement being between the inlet face of the filter cartridge and the housing surrounding wall to help hold the filter cartridge in sealing engagement with the housing. (a) the interior surface of the cover includes a receiver that contains at least a portion of the cartridge-handle when the filter cartridge is operably oriented within the housing interior and when the cover is secured over the access opening, (b) the filter cartridge includes a shell with first and second opposing shell walls (606, 607) secured to the media pack; the cartridge-handle projecting from the first shell wall; (c) the shell includes a frame extending between and joining the first and second shell walls; the frame being mounted against the second flow face of the media pack; the frame including: (i) a base member defining an airflow opening arrangement in communication with the second flow face; (ii) a seal support section extending from the base member along a perimeter of the airflow opening arrangement; (i) a base member defining an airflow opening arrangement in communication with the second flow face; (ii) a seal support section extending from the base member along a perimeter of the airflow opening arrangement; (d) the seal member is oriented against the seal support section; (e) the cover further includes a projection arrangement extending from the interior surface into the housing open interior, when the cover is secured over the access opening; (f) the projection arrangement includes at least first and second legs (645, 646) extending from the interior surface of the cover; and (g) the receiver is between the first and second legs and laterally spaced therefrom;