Air filter cartridges for use in air cleaner assemblies are described. The air filter cartridges typically comprise a stack of strips of fluted media, having an inlet flow face and an outlet flow face. A projection is provided extending outwardly from adjacent the outlet flow face of the media pack, as a projection supporting a seal arrangement. The seal arrangement is typically rectangular, with four straight and four rounded corners. The projection can be configured with open corners, and in some instances comprises tabs, to facilitate flexing of the projection to accommodate variations in a housing seal surface, with which the cartridge is installed. Air cleaner assemblies and components therefor, using cartridges in accord with the descriptions herein, are described.