Abstract: A brush seal is formed by bristles tightly packed between two annular sideplates having different inner radii and secured to a housing. The free ends of the bristles are in rubbing contact with a shaft. The differential pressure which the seal can support is increased by loading the bristles against the annular sideplate having the smaller inner radius, the loading force being such that the bristles can still move in the plane of the seal. As a result the amount of relative movement of shaft and housing that the seal can tolerate is not reduced.