A sealing member for sealing over an aperture in a surface. The member comprises a flange formed from a resilient material for sealing against the surface around the aperture in the surface. A strengthening member supports the flange. A retaining portion formed from the resilient material is provided on an outside surface of the strengthening member to secure the strengthening member to the flange. The retaining portion is integrally formed with the flange via a through hole in the strengthening member.