A filter cartridge which comprises a filter pack (3) formed by a flat filtering medium, a tubular sheath (2) with a perforated wall, surrounding the filtering pack, and two respective end caps (5) having a first disc (16) and a second disc (17) placed one on top of the other, each made from thermoplastic, with a portion of the filtering pack (3) situated along one of its edges and a portion of the sheath (2) situated along one of its edges (33) which are embedded in the second disc (17), with the first disc (16) having a peripheral rim (19) which surrounds the relevant portion of the sheath (2) and with the sheath having a shoulder (34) opposite the edge of the rim (19) of the first disc (16).