Abstract: An intracorporal probe has a flexible and generally nontwistable element having front and rear ends, a flexible and continuous sleeve substantially surrounding and loosely receiving the element between its ends, and a sensor unit mounted on the front end of the element past the sleeve and itself having a front end. Thus twisting of the rear end of the element will twist the sensor unit and will twist the element relative to the sleeve. A forwardly tapered and flexible tip is carried on the front sensor end and a balloon is engaged around the unit between the tip and the sleeve at the front element end. The tip is mainly formed of silicone of a hardness between 50 shore and 100 shore.