A device for use in measuring blood pressure comprises a cuff which is windable around the portion of a body and a clamp fastener for maintaining the cuff in the wound position during use. The fastener has a box shaped outer part and a box shaped inner part which is moveable therein perpendicular to the longitudinal access thereof and has slots in its end faces for receiving a pressure rod about which the cuff is looped. A sound pickup is disposed in the pressure chamber of the cuff and is connectable to a display instrument via an air tube.