Abstract: A variable flow restricting device comprises a part (12) having a groove (14) provided in a face (18) thereof and a through-passage (20) communicating with the groove. The device further comprises a covering structure (22) for engaging the face (18) to cover the groove (14) and thereby define a flow path which extends from the through-passage (20) in communication therewith. Covering of the groove is facilitated by a structure (26) for providing relative displacement between the part (12) and the covering structure (22) for causing resilient deformation of the covering structure and/or the part (12) to provide adjustably variable covering of the groove. The flow path extends from the through-passage (20) to an extent which is adjustably variable according to relative displacement of the part (12) and the covering structure.