O-rings are at the girth closed round sealing elements, whose mode of action is based on the deformation of the cross section. They are endlessly made of elastomer materials in forming tools through vulcanization. The simplicity of the form and the reliability of the function of a O-ring sealing is genious. Therefore, it is the most used sealing. The economical production and the easy installation make the O-ring unbeatable. The name of the O-ring consists of the dimensions of the inside diameter and the cord size in mm as well as the material name and its strength (elasticity).