A sealing wafer for use in an ostomy appliance is provided. The sealing wafer has an attachment platform with a distal surface capable of being attached to an ostomy bag, a proximal surface facing towards the user during use, and an opening having an inner boundary defining a stoma receiving opening. The sealing wafer further includes a fixed base member attached to the attachment platform and a rotating member arranged to rotate relative to the fixed base member. A sealing member is coupled between the fixed base member and the rotating member for providing a seal around a stoma and defining a stoma sealing orifice. When the rotating member is rotated relative to the base member, this rotation causes an increased or a decreased tension to be applied to the sealing member so that the diametrical dimensions of the stoma sealing orifice change from a first diameter to a second diameter. Thus a mechanical sealing member that can be used with one-piece ostomy appliances as well as with two-piece ostomy appliances is provided.