A probe unit for applying high level high frequency voltages to tissues to be treated has a tubular handpiece having an operative end and a female connector fixed at the operative end and connectable to a source of high level high frequency voltage. An interchangeable plastic nose piece, which can be conical or contra-angled in shape, includes a proximal end provided with a mating male connector electrically engageable with the female connector. An elongate conductor sleeve is in electrical communication with the male connector and extends to a distal end remote from the proximal end of the nose piece. A disposable probe tip, which includes a cutting tip, is configurated so as to be receivable in the elongate sleeve of the nose piece. The probe tip has an elongate insulating cylindrical shell having two axial slots. A resilient conductive wire, which forms part of the external cutting tip, extends partially interiorly of the shell to form two spaced opposing resilient arcuate portions which pass through the respective slots and which are depressible into the shell. In this manner, insertion of the shell into the sleeve depresses the arcuate portions to thereby provide frictional engagement and electrical contact between the cutting tip and the sleeve.