Abstract: A filter assembly or unit having end caps or fittings which are held together by tie rods with a filter casing between them and sealed to them. A filter cartridge is within the casing. Each end fitting or cap is constructed to provide a slideway to receive a sliding member that seals to the end fitting and which sealing engages an end of the filter casing. The sliding members can be secured to the end fittings. The sliding members along with the filter casing can be removed laterally from the assembly, the end fittings or caps remaining coupled in an air or gas line containing fluid to be filtered. In this manner the cartridge or cartridges can be replaced in the filter casing without uncoupling the end fittings from the an air or gas line and without disassembling the cage formed by the end fittings and the tie rods.