A slender, metal, tubular device that is coaxially attached to an ultrasonic lithotripsy system handpiece [a hand-held acoustic transducer that produces ultrasound (US) waves] and intended to transmit US waves to calculi (stones) in the urinary tract (i.e., kidneys, ureters, and bladder) for their fragmentation. Its distal end is brought into contact with calculi and transmits the energy, breaking down the calculi in the body for removal through its lumen. This device is introduced through the working channel of an appropriate endoscope (e.g., a percutaneous nephroscope for ureteral stones). This is a single-use device.