Abstract: An adjustable clamp for controlling the flow of fluid through a flexible tubing having deformable walls has an elongated, externally threaded body having an axial bore through which the tubing passes. One end of the body contains one or more longitudinally slots communicating with the bore, in which slot is located an elongated arm or wing hinged at one of its ends to the body, the other end of the arm being free to move radially within the slot. The radial height of the arm tapers, being a maximum at its free end and a minimum at its hinged end. A threaded nut engaging the thread on the body is provided with a bearing surface which contacts the tapered surface of the arm. As the nut is turned in a direction to move it towards the slotted end of the body, the arm is progressively forced into the slot, deforming the enclosed tubing to an increasing degree, thereby permitting control of the flow of fluid through the tubing.