An air filter cartridge comprising: (a) a media pack having first and second, opposite, flow faces (401, 402); a first pair of opposite sides (410, 411); and a second pair of opposite sides (414, 415); (i) the media pack comprising a stack of strips of single facer filter media material, each strip including a fluted media sheet secured to a facing media sheet and oriented with flutes of each fluted sheet extending in a direction between the first and second, opposite, flow faces (401, 402); so that the media operates as follows: first, air enters first flutes being open adjacent the first flow face; due to a closure of the first flutes at the second flow face, the air passes through the media, and then exits the media pack, by passage through open ends of second flutes, adjacent the second flow face of the media pack; (ii) the first pair of opposite sides (410, 411) comprising first and second sides (410, 411) extending between the first flow face and the second flow face and engaging the first flow face along first and second edges (401r, 401s); the first edge having a different length than the second edge; and, (iii) the second pair of opposite sides (414, 415) comprising third and fourth sides (414, 415) extending between the first and second opposite, flow faces (401, 402) and also between the first and second sides (410, 411); the second pair of opposite sides (414, 415) engaging the first flow face along third and fourth edges (401x, 401y); (b) a perimeter housing seal arrangement extending around the media pack; (c) a first side panel having at least 70% of a length of the first side between the first and second flow faces (401, 402) sealed thereto; (d) a second side panel having at least 70% of a length of the second side between the first and second flow faces (401, 402) sealed thereto. (a) a media pack having first and second, opposite, flow faces (401, 402); a first pair of opposite sides (410, 411); and a second pair of opposite sides (414, 415); (i) the media pack comprising a stack of strips of single facer filter media material, each strip including a fluted media sheet secured to a facing media sheet and oriented with flutes of each fluted sheet extending in a direction between the first and second, opposite, flow faces (401, 402); so that the media operates as follows: first, air enters first flutes being open adjacent the first flow face; due to a closure of the first flutes at the second flow face, the air passes through the media, and then exits the media pack, by passage through open ends of second flutes, adjacent the second flow face of the media pack; (ii) the first pair of opposite sides (410, 411) comprising first and second sides (410, 411) extending between the first flow face and the second flow face and engaging the first flow face along first and second edges (401r, 401s); the first edge having a different length than the second edge; and, (iii) the second pair of opposite sides (414, 415) comprising third and fourth sides (414, 415) extending between the first and second opposite, flow faces (401, 402) and also between the first and second sides (410, 411); the second pair of opposite sides (414, 415) engaging the first flow face along third and fourth edges (401x, 401y); (i) the media pack comprising a stack of strips of single facer filter media material, each strip including a fluted media sheet secured to a facing media sheet and oriented with flutes of each fluted sheet extending in a direction between the first and second, opposite, flow faces (401, 402); so that the media operates as follows: first, air enters first flutes being open adjacent the first flow face; due to a closure of the first flutes at the second flow face, the air passes through the media, and then exits the media pack, by passage through open ends of second flutes, adjacent the second flow face of the media pack; (ii) the first pair of opposite sides (410, 411) comprising first and second sides (410, 411) extending between the first flow face and the second flow face and engaging the first flow face along first and second edges (401r, 401s); the first edge having a different length than the second edge; and, (iii) the second pair of opposite sides (414, 415) comprising third and fourth sides (414, 415) extending between the first and second opposite, flow faces (401, 402) and also between the first and second sides (410, 411); the second pair of opposite sides (414, 415) engaging the first flow face along third and fourth edges (401x, 401y); (b) a perimeter housing seal arrangement extending around the media pack; (c) a first side panel having at least 70% of a length of the first side between the first and second flow faces (401, 402) sealed thereto; (d) a second side panel having at least 70% of a length of the second side between the first and second flow faces (401, 402) sealed thereto.