Abstract: An annular seal comprising a mass of bristles (10) packed together in a layer axially adjacent to an annular backing plate (12). The bristles (12) and backing plate (14) are mounted on and extend from a radially outer member (4) towards and around a cylindrical inner member (2). The outer (4) and inner (2) cylindrical members rotate relative to each other about an axis (1). The bristles (10) co-operate with the inner cylindrical member (2) to form a seal thereagainst. An expansion ring (18) is disposed radially inwardly of the backing plate (14) and is mounted in substantially the same plane from the backing plate (14) via a suitable mounting arrangement (16) which is arranged to permit radial movement of the expansion ring (18) relative to the backing plate (14) and the operational position of the inner cylindrical member (2).