The inner assembly (2) of a tube pressure filter comprises a core (6) provided with a facing (36) made up of a plurality of laths. At the end of the core (6) there is an annular member (42, 44) which is retained in position between the facing (36) and a split retaining ring (60, 62). The retaining ring (60, 62) fits in a groove (58) in the core and is locked in position by locking elements (64) which fit into aligned recesses in the retaining ring (60, 62) and the annular member (42, 44) and are secured by screws (68).