An ultrasonic transducer for an ultrasonic, flow measuring device comprising an electromechanical transducer element and an ultrasound window, wherein an adapting, or matching, layer liquid at operating conditions of the ultrasonic transducer is arranged between the electromechanical transducer element and the ultrasound window, wherein the ultrasonic transducer has holding means, which exert a releasable force toward the ultrasound window on the electromechanical transducer element, in order to hold the electromechanical transducer element in a predetermined position relative to the ultrasound window.