A retractable assembly and a sealing system, the sealing system comprising: an essentially hollow, cylindrical housing with an inner space and a peripheral groove open to the inner space in the housing. The peripheral groove defines a plane in the housing and the normal of the plane is parallel to the longitudinal axis of the housing. The groove includes at least one, preferably two, extension spaces expanding the groove. The extension space is arranged on the side of the groove facing away from the inner space. An annular seal corresponding to the groove is arranged in the groove. The annular seal is formed of at least a first section facing the inner space and a second section facing away from the inner space.