Except of sealing materials of General requirements, the seals would also like to note the following conditions: (1) flexible and resilient, (2) adequate mechanical strength, including tensile strength, elongation and tear strength. (3) stable, not in the medium swelling, thermal contraction (Joule effect) is small. (4) processing, and kept their accurate dimensions. (5) no contact corrosion, do not pollute the media and so on. Meet these requirements the most suitable and most commonly used material is rubber, so most sealing rubber material. Many varieties of rubber, and there are always new rubber varieties appear, design and selection, you should understand the characteristics of various rubber, reasonable choice.