In the last few years a great many changes and improvements have taken place in the technology of the sealing industry, particularly with regard to those seals which utilize elastomers to do the job. This sealing technology can be divided into three primary areas: materials, designs and testing procedures.In the material area, there have been a number of significant improvements in some of the older polymers. There have also been several new materials, both in the thermoset and thermoplastic varieties which have enjoyed substantial success.A great deal of emphasis has been placed on the development of superior exclusion devices. Also, a number of new improved packings have permitted operation at higher pressures and broader temperature ranges than was previously possible.A very significant development has been the formalization of a number of industry standards for the evaluation of these sealing devices. For the first time, it will be feasible for the user to evaluate performance characteristics of seals supplied by different manufacturers using the same yardstick.