Trelleborg Double Delta® combines the flexibility and response of O-Rings with the wear and friction characteristics of the Turcon® materials in dynamic applications. The double acting performance of the seal follows from the symmetrical cross section which allows the seal to respond to pressure in both directions. Initial contact pressure is provided by radial compression of the O-Ring. When the system pressure is increased the O-Ring transforms this into additional contact pressure, the contact pressure of the seal is thereby automatically adjusted so sealing is ensured under all service conditions.