A typical oil seal has a shaft diameter of 0.25 inch, an outer diameter of 0.75 inch, and a width of 0.25 inch. Another type of oil seal has a shaft diameter of 0.437 inch, an outer diameter of 0.624 inch and a width of 0.125 inch.
Oil seals are widely used in many manufacturing processes to serve as a barrier against leakage. Oil seals are made to accommodate the variety of different chemical, physical and temperature strains under which commercial and industrial equipment must function. They are designed with metric and inch measurements, and a designation of "20 47 7" inscribed on a seal denotes an interior diameter of 20 millimeters, an outside diameter of 47 millimeters and a width of 7 millimeters.