A filter insert (10) comprising: a body portion (12) and a closed-ended tube (14), an open end of which is sealingly affixed around the periphery of the body portion (12); an inlet aperture (16) and an outlet aperture (18) each aperture communicating via a through hole in the body portion (12) with the interior of the tube (14); a filter medium (20) located within the tube (14) and being sealingly interposed between the inlet aperture (16) and the outlet aperture (18), wherein the tube (14) is at least partially manufactured of a flexible plastics material, and wherein the body portion (12) is relatively rigid.