1. A swivel insertable into a drill or work string comprising:
(a) a mandrel having upper and lower end sections rotatable with upper and lower drill or work string sections, the mandrel including a longitudinal passage forming a continuation of a passage in the drill or work string sections;
(b) a sleeve being rotatably and reciprocably with respect to the mandrel;
(c) a plurality of packing units between upper and lower end portions of the mandrel and the sleeve, the plurality of packing units preventing leakage of fluid between the mandrel and the sleeve, at least one of the packing units in the plurality of packing units comprising a lubricating seal, wherein the plurality of packing units include a seal comprising metal filled teflon.