Abstract: A seal (10, 12) having a mating ring (100, 100?) mounted in a fixed axial and rotational relationship with respect to a shaft (14) and a primary ring (120, 120?) mounted in fixed rotational relationship but movable axially with respect to a housing assembly (16). Springs (136) are provided to urge the primary ring (120, 120?) axially into sealing engagement with the mating ring (100, 100?). The mating ring (100, 100?) are mounted with respect to the shaft (14) in abutment with a first radial face (44, 62). A circumferential surface of the mating ring (100, 100?) is spaced radially from a circumferential surface on the shaft (14) and an annular helical spring element (104) is located, under radial compression, between the circumferential surfaces. The annular helical spring element (104) is formed from wire of elongate section, the axial width of the section being greater than the radial thickness.