Abstract: A seal (30) is provided for reducing the gap between alternate wall members (20) and adjacent blades (14) that are arranged circumferentially in a rotor (12). The seal (30) has a flange portion (36), which is inclined radially inward. The flange portion (36) of the seal (30) is in the form of rubber bellows (32) which have a cavity (34) therein. In operation the flange portion (36) of the seal (30) is deflected radially outwards by centrifugal forces acting thereon. The seal (30) is open at one end to allow air compressed by the rotor (12) to pass into the cavity (34) and inflate the seal (30). Inflation of the seal (30) ensures that the gap between the edge (26) of the wall member (20) and the blade (14) is filled. A good seal is thus maintained throughout operation of the rotor (12) and prevents the air in void (28) passing into the blade passage.