Abstract: A filter for filtering fluids, in particular gas in petrochemical plants, has: a tubular cartridge which extends along a first axis, is designed to filter a fluid, and has a first and second annular end; a casing, which is connectable to a conduit of a petrochemical plant, houses the tubular cartridge, and has a first and second end support; and an axial compensating ring located between the tubular cartridge and the first or second end support.