If the O-ring and the retaining ring are used to seal, because the O-ring needs to be compressed, the retaining ring cannot be compressed. When choosing the O-ring and the retaining ring, whether the outer diameter is the same or the inner diameter is the same. If the inner diameter is the same, what is the difference between the outer diameter of the O-ring and the retaining ring? 1. There are two national standards for the O-ring: GB1235 GB3452 The former is an old standard, but it is still widely used. For the selection of O-ring or retaining ring, please refer to the detailed regulations of the standard, and select and use according to the standard. 2. O-ring GB1235-76 standard and retaining ring, the first Ministry of Machinery Industry (First Machinery Department) has previously formulated the standard and is used in major hydraulic parts manufacturers. The outer diameter shall prevail, and it is widely used. The GB3452 series of standards seems to be gradually popularized and used after the introduction of German technology. Especially used in combination seals (Grey ring and step seal). Now there are two kinds of sealing standards, and there are detailed standard provisions in the manual.