Filter cartridge arrangements, features thereof and assembly for use therewith, are provided. Selected filter cartridge features disclosed are particularly well adapted for use with a safety or secondary filter cartridge, usable with media thereof projecting into an open interior of a main filter cartridge, in use. An example filter cartridge is described, with a non-pleated end and a pleated end, although variations are also described. Advantageous main cartridges are also described. Methods of assembly and systems for use are described.