A brush for sealing a gap between a rotor/stator system comprises a rotor-concentric clamping ring whose interior chamber receives bristle bundles that project into gap. The bundles are wrapped around core ring that extends into the interior of clamping ring. The core ring has separating disks that are spaced apart from one another in the circumferential direction by an angular pitch .alpha., and by winding ribs that are wrapped by the bundles. The winding ribs connect adjacent separating disks in such fashion that as a result of the diagonal positioning of separating disks in the circumferential direction, bundles are aligned at an angle .beta. to radius R. This makes it possible to hold bristle bundles securely with a predetermined angular orientation.