O-Rings are the most commonly used seals. It will cause oil leaking accident if selection, groove design, processing and installation are not well. It may be said small elements make big thing bad.
O-Rings dimensions mainly have American standard and Japanese standard, AS568 and P,G code.
The main material of O-Rings are NBR and FKM. FKM used for high temperature.
Except material, hardness is very important for O-Rings, it usually use shore A unit. From 60 to 90 shore A. The hardness is higher if the numerical value is bigger. The extrusion resistance is better if hardness is higher under the same pressure. The resilience is better if hardness is smaller.
Usually the O-Rings of 70 shore A hardness used for industry. 90 shore A hardness used for construction machinery.