Abstract: A spacer for an endodontic instrument includes a base surface with a diameter dG, a top surface with a diameter dD, which is smaller than the diameter dG, an axis of rotation, a lateral surface, a height h, an opening with a longitudinal axis for receiving an endodontic instrument and a cylindrical recess for receiving a stopper on the base surface. The spacer is frustoconically formed, and the opening extends from the base surface to the top surface. The longitudinal axis of the opening is coaxial to the axis of rotation of the spacer, and the cylindrical recess is coaxial to the opening.