A mechanical assembly includes a shaft having a central axis and an outer member having a bore disposed about the shaft, either the shaft or the outer member having a gland defined by a circumferential surface and at least one radial surface and the other one of the shaft and the outer member being angularly displaceable about the central axis. A seal has an annular body disposed within the gland and is formed of an flexible material, preferably a plastic or elastomeric material, the annular body having a main body portion with inner and outer radial ends. An inner sealing lip extends radially inwardly from the inner end of the main body portion and is configured to engage with the shaft. An outer sealing lip extends radially outwardly from the outer radial end of the main body portion and is configured to engage with the outer member.