Abstract: A radial lip seal comprises a rigid casing ring (10") and a rubbery sealing element (12") secured to the ring. An inner portion (13") of the element forms a sealing lip (14) for engagement with a shaft (S). Adjusting means, enabling variation of the bore of the seal, comprises an annular adjusting member (17") which moves axially upon rotation about the seal axis. The member comprises a mounting portion (18") and an inner portion forming an axially-projecting bearer (19") which abuts the sealing element adjacent to the lip (14). Four camming tongues (22) project outwards from the casing ring to engage in slots (24) in the adjusting member (17"), the tongues being angled so as to cause controlled axial displacement of the member with rotation. A stop tongue (26) engaging in a gap (27) in the adjusting member limits the range of adjustment.