An ultrasonic flow meter permitting easy insertion and removal of a tube or conduit. A partial ring transducer or partial cylinder transducer is used to permit easy insertion and removal of a flexible tube in an ultrasonic flow meter for measuring fluid flow. In another embodiment a split ring or split cylinder transducer is used to facilitate easy removal and insertion of a tube or conduit in which fluid flow is to be measured. In another embodiment a clamping system is used to securely hold and couple a tube or conduit within the ultrasonic flow meter system. The present invention is conveniently adapted to hold flexible tubes and in particular disposable flexible tubes often used in the medical industry.