Abstract: The present invention involves a seal ring for sealing an annular space between two components. The seal ring includes an annular jacket, a spring, and a cap. The jacket includes an annular cavity defined by two annular lips. The spring is disposed within the annular cavity of the jacket. The cap is disposed over the annular lips, and encapsulates the annular cavity. The spring biases the lips against the cap to thereby seal the annular cavity. Either the cap or the jacket includes a pair of annular channels, and the other includes a pair of annular projections, so that the projections and channels interfit to thereby lock together the cap and jacket. The cap and jacket are made from a polymer material, although not necessarily the same polymer material. The spring may be cantilevered, helical ribbon coil, slanted coil, or silicone filled with one or more spring elements. The lips of the jacket may have flanges to trap the spring in the annular cavity.