a seal ring for sealing an annular space between two telescoped and relatively movable parts . the ring seats in a groove in one of the parts , and leaf springs urge the seated ring against the other part to effect the seal . the leaf springs include annealed or reduced - cross - section portions which provide relatively low - rate and long - travel spring characteristics to accommodate tolerance variations , dimensional changes of the ring as wear occurs , and thermal expansion or contraction of the sealed parts . the wearing surfaces of the ring may be covered by a plastic cap or anti - galling coating .