A screw assembly comprising: a screw shaft having a helical thread profile; and a nut for mounting around said screw shaft; the screw assembly further comprising a first seal and a second seal, wherein each of said first seal and said second seal independently comprises a seal of the type comprising: a seal body having an inner surface for mounting onto and sealing against a screw shaft; an internal chamber formed within said seal body, wherein one or more openings are provided on said inner surface to allow lubricant material to transfer between said inner surface and said internal chamber; and one or more external ports provided on a radial surface and/or an outer surface of said seal body for transferring lubricant material into or out of said internal chamber of said seal body; characterized in that respective external ports (27A, 27B) of said first and second seals (26A, 26B) are each aligned with a respective passage formed within said nut, the passage(s) extending through said screw assembly to provide a re-circulating path for re-circulating lubricant material within said screw assembly, and in that the re-circulating path extends from the first seal through the passage(s) formed within the nut to the second seal. a screw shaft having a helical thread profile; and a nut for mounting around said screw shaft; the screw assembly further comprising a first seal and a second seal, wherein each of said first seal and said second seal independently comprises a seal of the type comprising: a seal body having an inner surface for mounting onto and sealing against a screw shaft; an internal chamber formed within said seal body, wherein one or more openings are provided on said inner surface to allow lubricant material to transfer between said inner surface and said internal chamber; and one or more external ports provided on a radial surface and/or an outer surface of said seal body for transferring lubricant material into or out of said internal chamber of said seal body; characterized in that respective external ports (27A, 27B) of said first and second seals (26A, 26B) are each aligned with a respective passage formed within said nut, the passage(s) extending through said screw assembly to provide a re-circulating path for re-circulating lubricant material within said screw assembly, and in that the re-circulating path extends from the first seal through the passage(s) formed within the nut to the second seal. a seal body having an inner surface for mounting onto and sealing against a screw shaft; an internal chamber formed within said seal body, wherein one or more openings are provided on said inner surface to allow lubricant material to transfer between said inner surface and said internal chamber; and one or more external ports provided on a radial surface and/or an outer surface of said seal body for transferring lubricant material into or out of said internal chamber of said seal body; characterized in that respective external ports (27A, 27B) of said first and second seals (26A, 26B) are each aligned with a respective passage formed within said nut, the passage(s) extending through said screw assembly to provide a re-circulating path for re-circulating lubricant material within said screw assembly, and in that the re-circulating path extends from the first seal through the passage(s) formed within the nut to the second seal.